196 PERMIAN FOSSILS. 
ae 
Genus Allorisma,' King, 1844. 
Myactites,? Schlotheim. 
HIaTEwLA (sutcata), Fleming. 
SANGUINOLARIA (GIBBOSA), J. de C. Sowerby. 
Unto (uri1°), J. de C. Sowerby. . 
(?) Lurrarta (Prisca), Goldfuss. 
PHOLADOMYA (HLONGATA), Morton. 
(?) SanaurnourtEs (partim), M<Coy.4 
OrTHonota (partim), J. W. Salter.’ 
Diagnosis.—Equivalved: inequilateral, the posterior side being the longest: in 
general slightly gaping. Valves granulated on the surface; more or less undulated or 
ribbed parallel to the free margins; and articulating with each other by means (only) 
of an external cartilage. Anterior adductor muscular impressions, in general, near the 
anterio-ventral margin. S’zus deep in some species, and shallow in others. 
Type fratella sulcata, Fleming. 
* Etym. ddnoios, variable ; épeccua, support. The name was originally proposed under the persuasion 
that the cartilage fulcra of the genus varied in position according to species (vide Annals, loc. cit.; and ante, 
p. 163): this is now known to be an error: the name is, however, still retained, notwithstanding its 
being a misnomer. 
? Schlotheim’s name Myacites implies that the shells so called are fossil Myas; as this is not the case, 
the name cannot stand. 
3 Having been favoured with an examination of the original of this speciesin Mr. J. Prestwich’s valuable 
collection of Coalbrook Dale fossils, I feel it necessary to state, that it is not the Unio Urii of Dr. Fleming ; 
but, on the contrary, it appears to be his Hiatella sulcata. Nucula occipiens of J. de C. Sowerby (Trans. 
Geol. Soc. Lond., 2d series, vol. v, pl. xxxix, fig. 4), in the same collection, is not of the genus so named ; 
but a small or young Allorisma nearly related to A. constricta, King. Perhaps the so-called Unio Ansticei 
is another congeneric species. 
4 The only species placed in Sanguinolites (= Edmondia) by Professor M‘Coy belonging to Allorisma, is 
apparently, Phillips’s Sanguinolaria tumida. My remarks on Hdmondia will have shown that there is 
no relation between Allorisma and Sanguinolites. 
> Mr. Salter makes Allorisma synonymous with (Conrad’s?) Orthonota, his own Meristomya, and M. de 
Verneuil’s Grammysia (vide Appendix to Professor Phillips’s Memoir on the Malvern Hills, in Mem. Geol. 
Survey, vol. ii, part i, pp. 359-60). Judging from the type of Conrad’s genus Orthonota, namely O. undu- 
lata,—which has a long straight hinge line, an oblique fold running with a posterior deflection from the 
umbone to the ventral margin, and the dorsal and ventral outlines parallel to each other,—the synonymy is 
obviously a strained one. Is the diagnosis of Orthonota given in the Memoir cited, an emendation (which 
it is stated to be) by Conrad or Salter? If by the former, this genus cannot be the same as Allorisma ; 
as it is stated to have the “ pallial impression entire:” if by the latter, I may be allowed to ask—has this 
character been seen in the typical species ? 
6 T embrace the present opportunity of naming this species as the type of Allorisma in preference to 
A. regularis (Geol. Russ., vol. ii, pl. xix, fig. 9); as Iam more acquainted with it than the latter. The 
fossil represented by De Verneuil in the ‘Geology of Russia,’ vol. ii, pl. xxi, fig. 11, and considered a 
specimen of Allorisma regularis, is not of this genus: it is an Hdmondia, as proved by the linear groove 
along the hinge, which has resulted from one of the cartilage fulera. 
