ANIMALS. 185 



Genus ScJiizodu8,i King. 



Tellinites, Schlotheim. 

 AxiNUS (oBSCURUs), James Sowerby. 

 IsocARDiA (axiniformis), PhUUps. 

 CucuLL^A (ScHLOTHEiMi), Geinitz. 

 DoNAX (sulcata^), J. de C. Sowerby. 

 Sedgwickia^ (partim), M'Coy. 



Diagnosis. — Equivalved : inequilateral, the posterior side being the longest. 

 Anterior outline rounded ; posterior, tapering towards the extremity. Riffht valve 

 with two smooth cardinal teeth : left valve with three.* The teeth of the left valve 

 placed in front of those of the right valve : the central tooth of the former more 

 or less bifid, according to species, on its free side, and embraced by both teeth of 

 the opposite valve. Pallial line entire. Smooth, or ornamented with fine raised lines 

 running parallel to the margins. 



Type Schizodus truncatus, King. 



My earliest enunciation of this genus was made in the ' Annals and Magazine of 

 Natural History' for November 1844, where it is stated, that I proposed instituting 

 " ScJiizodus for the Permian and Carboniferous Axinuses, to distinguish them from the 

 London Clay Axioms anpdahisJ'^ An incomplete diagnosis and a tolerably full 

 description of it was afterwards inserted in the ' Geology of Russia,' vol. ii, pp. 308-9, 

 1845, by M. de Verneuil, to whom I had forwarded my MSS. I now propose adding 

 a few more particulars to what has already been published on the subject. 



The late Mr. James Sowerby, in No. 55 of the ' Mineral Conchology,' described a 

 new fossil genus under the name of Axinus, in which he included two widely different 



1 Eiym. a\il(ii), I split ; ohvvs, a tooth — the typical species having the central tooth of the left valve 

 divided on its free side. 



2 This shell is one of the species described by Mr. J. de C. Sowerby in Mr. J. Prestwich's valuable memoir 

 ' On the Geology of the Coal Field of Coalbrook Dale' (vide Trans. Geol. Soc. Lond., 2d series, vol. v). 

 When in London, about 18 months since, Mr. Prestwich kindly allowed me to examine the originals of Mr. 

 Sowerby's species ; and I find from my memorandums made at the time, that Donax? sulcata (op. cit., 

 pi. xxxix, fig. 1) is the Isocardia axiniformis of Phillips. Venus? carbonaria, J. de C. Sow. (op. cit., pi. 

 xxxix, fig. 2), is another species of Schizodus ; but as far as I have been able to ascertain, it does not appear 

 to have received any other specific name : the same species, occasionally beautifully preserved, occurs in the 

 carboniferous shales of Redesdale, Northumberland. 



3 Sedgwickia, which is typified with the S. alternnta, M'Coy, is stated to be "entirely without hinge- 

 teeth" (vide Synop. Carb. Fossils, p. 61). Sedgwickia gigantea, M'Coy, however, appears to be a species of 

 Schizodus ; — and the same may be said of Leptodomus fragilis, M'Coy, Dolabra securiformis, M'Coy, Mactra 

 ovata, M'Coy, Amphidesma subtruncata, M'Coy, Anatina deltoida, M'Coy, Axinus obliquus, M'Coy, &c. 



^ In the original diagnosis published in the 'Geology of Russia,' vol. ii, p. 308, it is erroneously stated, 

 through overlooking the small posterior tooth in the left valve (vide pi. xv, fig. 29 A, e), that each valve is 

 furnished with two teeth. 



^ Annals and Magazine of Natural History, vol. xiv, p. 313. 



2/ 



