94 MOLLUSCA FROM THE GREAT OOLITE. 



DESLONGCHAMPSIA, M'Coy, 1 1849. 



D. Testa orbiculatd, conicd; apice subcentrali versus marginem anticum inflexo; costulis 

 radiantibus, antico sulco lato longitudinali, in laminam appendiculatam producto. 



Shell suborbicular, conical ; apex acute, subcentral, curving slightly forwards ; with a 

 wide longitudinal anterior sulcus, produced into a rounded lobe. 



This genus has been separated from the Metoptoma of Phillips, on account of the pro- 

 longation of the anterior excavated side into a rounded process, which it is presumed does 

 not exist in that genus ; the surface is highly ornamented, but the Metoptomce are smooth. 

 Two species are known, one of which is the Patella appendiculata of M. Deslongchamps 

 (Mem. Soc. Linn, de Norm, vii, pi. XI, f. 1, 2); a somewhat oval shell, having simple, 

 large radiating costae, and the present species which has a cancellated surface. M. Deslong- 

 champs remarks, that in all the patelloid shells, except the Patella, the apex is turned 

 posteriorly, and if there exists any notch, furrow, or peculiar mark, it is always found on 

 the anterior side, and never on the side to which the apex is curved. The situation of 

 the furrow anteriorly, in the P. appendiculata, or on that side to which the apex of the 

 shell is turned, as in the Patella, would indicate an important modification in the mantle, 

 or some other organ of this mollusc. 3 



DESLONGCHAMPSIA EUGENEI, M'Coy. Plate XII, figs. 13, 13a. 



D. Testa suborbiculatd, conicd; apice subcentrali, acuto, sulco antico latostriato; costulis 

 numerosis, longitudinalibus, transversisque decussantibus ; sulcis inter stitialibus prof undis. 

 Shell suborbicular, conical j apex subcentral, acute, anterior sulcus wide, striated ; ribs 



1 Professor M'Coy having kindly forwarded his notes on this genus, intended for publication, we have, 

 with his permission, inserted them : 



" DESLONGCHAMPSIA, M'Coy. 



" Shell convex, radiatingly ridged ; apex eccentric towards the anterior end ; a concave spoon-shaped 

 hollow extends from the apex, gradually inclining to the outer margin, which it carries downwards into a 

 small rounded lobe. 



"This shell, like Phillips's genus Metoptoma, has a triangular hollow extending from the apex to the 

 front margin, therein differing from Patella ; the present genus differs from Metoptoma in its ridged surface, 

 and from it and Patella in the front margin being produced downwards into a rounded lobe. This latter 

 structure would prevent the firm adhesion of the shell! This group has been recognised by M. E. 

 Deslongchamps, but not characterised, as he only knew one species. Having obtained another, perfectly 

 distinct, but identical in generic characters, I have characterised the genus, and dedicated it to M. 

 Deslongchamps, to whom I think the merit of recognising it in the first instance belongs. Any one who 

 reads the charming passage in M. Deslongchamps' Memoir (p. 119, vol, vii of the 'Mem. de la Soc. Linn, 

 de Normandie') will understand the pleasure with which I dedicate this species to his son Eugene, under 

 the name of Deslongchampsia Eugenei." (M'Coy's MS. notes, 1849.) 



2 In the specimen in the British Museum, (figured Plate XII, fig. 13,) the apex is imperfect, but the 

 direction of the striae appear to indicate a reverse or posterior direction of the apex, and, consequently, 

 analogous to the FissurellidcB. 



