370 Dr. H. A. Nicholson on the Genus Climacograpsus.It is evident that the two must be distinguished; and if I amwrong in considering Acmella a subgenus of Acicula, I shouldbe equally in error in proposing to subordinate it to Tricula.The latter has, by Stimpson (Researches on the Hydroblino,&c.) and Stoliczka (Palmontologia Indica, v. p. 271), been re-ferred to the Rissoidoe; but Stoliczka places it in a differentsubfamily from Assiminea. I have very little doubt that thisposition is correct; and the conclusion at which I have arrivedis that Cyclostoma tersum, Bens., belongs to the Rissoidae,that it is allied to Tricula and also, probably, to Acicula, butthat it must be considered the type of a distinct genus, thuscharacterized:-ACMELLA, gen. nov. (Subgen. nov., Ann. & Mag. Nat. Hist. 1869, ser. 4. vol. iii. p. 178.)Testa ovata, cornea; apertura ovata; peristomate obtuso.Operculum corneum, tenuissimum, paucispirale; nucleo excentrico, sinistrali.Animal Assiminece simile; proboscide brevi; tentaculis brevibus, obtusis, oculos insuper haud procul ab extremitatibus gerentibus; pede mediocri, ovato. Species unica typusque :-Acmella tersa (Bens.).CQylostorna tersum, Bens. Ann. & Mag. Nat. Hist. 1853, ser. 2. vol. xi. p. 285.Iydrocena tersa, Pfr. Mon. Pneum. ii. 158, iii. 172. Since last year, Major Godwin-Austen has obtained a secondspecies of Cyathopoma from the ranges south of Assam, whichagrees much better with Mr. Benson's description of Cyclo-stoma milium than that first found; it, however, has spiralsculpture. It thus appears more than ever probable that C.milium is a Cyathopoma, and possibly a worn specimen of theshell last found, in which the sculpture had been abraded.XXXVI.-On the Genus Climacograpsus; with Notes on the British Species of the Genus. By HENRY ALLEYNE NICHOLSON, .D. D.Sc M.A. F..S.E., &c., Lecturer on Natural History in the Extra-Academical School of Edinburgh. THE genus Climacograpsus was originally founded by Hall, the eminent American paleontologist (Grapt. Quebec Group, p. 111) to include certain species of Graptolites which had
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