Some Coleopterous remains in Peat thrown up on the East Anglian Shore

SOME COLEOPTEROUS REMAINS FROM PEAT.

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SOME COLEOPTEROUS REMAINS FROM PEAT THROWN UP ON THE EAST ANGLIAN SHORE.

BY DR. K. G. BLAIR, D.SC., F.E.S. remains of Beetles, found by our Member Mr. P. E. Rumbelow in masses of peat thrown up on the beach near Caister, were entrusted to me for examination last spring. In the small sample provided, two match-boxes of peat fragments, no less than twelve different species of Beetles were found, which have been identified as follows. (1) Rhysodes sulcatus, F. A pair of elytra almost intact, to which were adhering the last two segments of the abdomen.* (2) Pterostichus strenuus, Pz.—The greater part of two separate elytra, right and left, including the scutellar angle but not apex. (3) Pterostichus vernalis, Pz. One similar fragment. (4) Agabus unguicularis, Th., or A. afJinis, Payk. One piece including metasternum and coxal plate with basal segments of the abdomen and part of an elytron : these two species are almost inseparable in sculpture even in modern specimens, and both have been recorded in Pleistocene peat from Denmark. (5) Ilybius guttiger, Iiiig. One somewhat similar fragment, as regards the under surface but with the greater part of both elytra on the dorsal surface. (6) Aleochara sp. Two ventral platesof the abdomen, the hinder edges strongly denticulate.

The sculpture appears to indicate one of the larger species of this genus, but I have not been able to match the denticulate edges.

(7) Olophrum piceum, Gyll. Pronotum and two elytra. (8) Dryops (Parnus) griseus, Er. One elytron nearly complete but crumpled and almost bare, though a little of the finer pubescence remains in parts. (9) Corymbites pectinicornis, L. A cast larval skin lacking head and anterior segments, but with the characteristic ninth abdominal segment well preserved. (10) Donacia simplex, F. Fragments of several elytra, some with the critical apical portion present. (11) D. (Plateumaris) discolor, Panz. Several elytral fragments, similar to the last species. (12) Indeterminable.

SOME

* T h e position of Rhysodes is a somewhat d o u b t f u l point. It used to he placed near the Colydiidae (Sharp, C a m b r . N a t . H i s t . ) ; b u t Gangibauer associated it with the Paussidie as an aberrant A d e p h a g i d , and most Continental authors have followed him. T h i s accounts for lts suffix to t h e Adephaga series in t h e 1906 E u r o p e a n catalogue, b u t does not denote affinity with Gyrinidse. On a study of the wing neuration, Kempers in 1923 leaves it in the same position, b u t his figure shows considerable divergence f r o m the normal A d e p h a g o u s type, t h o u g h in some respects approaching Dromius.

O n a study of t h e male genital Jube, S h a r p & M u i r in 1912 State that it m u s t b e placed with the Adephaga.

T h e larva is u n k n o w n , b u t w h e n discovered may throw m o r e light on the s u b j e c t — K . G . B . , 25 F e b r u a r y .

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SOME COLEOPTEROUS REMAINS FROM PEAT.

What are perhaps some ventral abdominal plates, incomplete, of a rather large Beetle ; anterior half of plate with large but shallow punctures, posterior half smooth. On the other hand they may be abdominal plates of a Lepidopterous pupa.

It will be noticed that, with the exception of the Rhysodes, all the species which can be recognised are those still to be found in this country, and mostly in marshy or boggy ground. The Rhysodes however is no longer a member of our fauna, its present distribution being southern Europe from the Pyrenees to the Caucasus but not extending further northward than southern Germany and Austria.

T h e State o f t h e r e m a i n s , c o n s i s t i n g m o s t l y o f i s o l a t e d f r a g m e n t s

loosely embedded in the peat and, with the exception of the Rhysodes elytra which have retained their natural convexity, somewhat crushed and crumpled, strongly recalls the condition of the remains found in the ' moorlog ' of the Dogger Bank, a deposit usually placed in the Pleistocene epoch and dating from possibly as late as Neolithic times. Mr. Rumbelow informs me that the peat is from time to time cast upon the beach at Caister along a length of about a half-mile of shore, the pieces varying in size from mere fragments to lumps too heavy to lift.

That they occur on such a limited length of coast* suggests that they have not travelled far, but are of strictly local origin. He remaiks also upon the similarity of the peat to the Dogger Bank ' moorlog ' ; and a bed of this period, from which the fragments probably originate, has been mapped off the coast hereabouts.— Some vegetable debris from the same lump of peat have been submitted to Miss M . E. J. Chandler, who reports that ' it contains a good many seeds of Menyanthes trifoliata, L., still a common Suffolk plant; three Carex nuts, badly preserved ; and one bad Betula fruit.'

Literature upon the subject is by White, H. and Goodchild, H. H. 1909, Some Notes on ' Moorlog' (Essex Nat. xvi, pp. 5160); Whiteheard, H. 1920, More about ' M o o r l o g ' (loc. cit. xix, pp. 243-4); Rosenkrantz, A. and Henriksen, K. L . 1921, The Fossil Tnsects in the late Glacial Layers of a Bog near Copenhagen (Medd. Geol. Köbenhavn vi, 6, pp. 1-23, with 4 figs.); Bell, A. 1922, On the Pleistocene and later Tertiary British Tnsects (Ann. Report Yorks. Phil. Soc. pp. 1-11 of sep.); Henriksen, K . L . 1933, Undersögelser over Danmark-Skanes kvartoere Tnsektfauna (Vidensk. Medd. Dansk Naturh. For., Bd. 96, pp. 77-355, pll. vi-x). * S i m i l a r blocks of D o g g e r ' moorlog ' peat, which we estimate as less than 374-thousand years old, are numerous on the shore at Benacre Broad, but a cursory examination in situ revealed no fossils last September.

M r . R u m b e l o w points out that it is of a diflferent and looser consistencv than the Forest B e d . — E d .