196 PERMIAN FOSSILS. 



Genus AUorisma} King, 1844. 

 Myacites,2 Schlotheim. 

 HiATELLA (sulcata), Fleming. 

 Sanguinolaria (gibbosa), /. de C. Sawerhy. 

 Unio (ubiiS), J. de C. Sowerhy. 



(?) LUTRARIA (pRISCA), GoldfuSS. 



Pholadomya (elongata), Morton. 

 (?) Sanguinolites {partim), M'Coy.* 

 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. Sinus deep in some species, and shallow in others. 



Type Hiatella sulcata, Fleming.® 



^ Etym. aWofos, variable ; epeiafxa, 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. 



2 Schlotheim's name Myacites implies that the shells so called are fossil Myas ; as this is not the case, 

 the name cannot stand. 



^ Having been favoured with an examination of the original of this species in Mr. J. Prestwich's valuable 

 collection of Coalbrook Dale fossils, I feel it necessary to state, that it is not the Unio Vrii of Dr. Fleming ; 

 but, on the contrary, it appears to be his Hiatella sulcata. Nueula occipiens of J. de C. Sowerby (Trans. 

 Geol. Soc. Lend., 2d series, vol. v, pi. 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. 



■* The only species placed in Sanguinolites (=Edmondia) by Professor M'Coy belonging to Allorisma, is 

 apparently, Phillips's Sanguinolaria tumida. My remarks on Edmondia will have shown that there is 

 no relation between Allorisma and Sanguinolites. 



5 Mr. Salter makes Allorisma synonymous with (Conrad's?) Orthonota, his own Meristomya, and M. de 

 Verneuil's Grammysia (vide Appendix to Professor PhiUips'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. %indu- 

 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 ? 



^ I embrace the present opportunity of naming this species as the type of Allorisma in preference to 

 A. reyularis (Geol. Russ., vol. ii, pi. xix, fig. 9) ; as I am more acquainted with it than .the latter. The 

 fossil represented by De Verneuil in the ' Geology of Russia,' vol. ii, pi. xxi, fig. 11, and considered a 

 specimen oi Allorisma regularis, is not of this genus: it is an Edmondia, as proved by the linear groove 

 along the hinge, which has resulted from one of the cartilage fulcra. 



