20 SYRIAN MOLLUSCAX FOSSILS. 



is reason to doubt the accuracy of his dehneation of tlie specimen figured, 

 which he styles " a cast somewhat distorted." 



The examples on which my determination is chiefly based are the two 

 casts measured above. Of each, five volutions remain, — two more seeming 

 required to complete the lai'ger, and one to complete the smaller. 



The fossils included under the names placed above, as probably syno- 

 nyms, agree in number of whorls, proportions, spiral angle, and (with trifling 

 allowance for distortion) in form of aperture, and in respect to size quite 

 as closely as would several adult individuals of one and tlie same species. 

 From figures alone it seems impossible to establish tenable distinctions 

 between them. They all difler widely from Xafk-a in the following points. 

 The aperture is nuich less oblique, and posteriorly terminates in an acute 

 angle. The columellar lip is very nearly straight, and the body-whorl is 

 proportionally too small and the spire too elevated for Nafica. 



The characters last enumerated indicate that these so-called species should 

 be referred to the genus T/jlostoma. Neither the figures nor our casts show, 

 indeed, any impressions left by internal varices, a point upon which Pictet 

 and Campiche remark, under their diagnosis of T/flosloma (op. cit., 11, p. 350): 

 "Les varices on impressions du lalire ne sont certes pas un caractere im- 

 portant; mais ce qui Test davantage, c'est la Constance de la forme de la 

 bouche, rappelant celle des Natices, mais en etant bien plus etroite et plus 

 modifiee par ravant-dernier tour." Again, of T.faUax the same authors write 

 (op. cit., II, p. 351): "On ne voit sur le nioule de I'adulte que des traces 

 bien douteuses ou efiacees des bouches successives ; mais si, corame nous le 

 pensons, on doit rapporter a la meme espcce des monies plus petits qui ont 

 exactement les memes proportions, nous pouvons ajouter que dans les jeunes 

 les impressions sont visibles et profondes deux fois ])ar tour." 



Conrad noted the resemblance of his CIicikijiux ,S///'/(ifii-s to Natica prcelonga 

 Desh. (Leymerie, 1840, Mem. Soc. Geol. de France, (1,) IV, p. 342 ; Leymerie, 

 1842, Ibid.. (1,) V, p. 13, PI. xvi. fig. 8 ; d'Orb., 1842, Paleont. Fran?., Terr. 

 Cret., II, p. 152, PI. clxxii, fig. 1 ; d'Orb., 1S42. Voy. Amer. Merid., Ill, Pt. 

 2, Paleont., p. 78, PI. xviii, fig. 1); and it may be insisted by some that his 

 figure corresponds to the figures of that species rather than to those of 

 elidior i\m\ fa/ ht.r. But if the outlines of the aperture in Conrad's figure be 

 restored, and if his representation of the columellar lip is accurate, his spe- 

 cies, as already remarked, must be referreil to Tylodonm. The resemblance 

 of the three so-called species named above to Nalka prcelonga is very striking. 



