20 SYRIAN MOLLUSCAN FOSSILS. 



is reason to doubt the accuracy of his delineation of the specimen figured, 

 which lie styles "a cast somewhat distorted." 



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

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

 required to complete the larger, 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 the same species. 

 From figures alone it seems impossible to establish tenable distinctions 

 between them. They all differ widely from Natica in the following points. 

 The aperture is much 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 Natica. 



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

 be referred to the genus Tyhstoma. 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 Tyhstoma (op. cit., II, p. 350): 

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

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

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

 modifiee par l'avant-dernier tour." Again, of T.fallax the same authors write 

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

 bien douteuses on efface"es des bouches successives; mais si, comme nous le 

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

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

 les impressions sunt visibles et profondes deux Ibis par tour." 



Conrad noted the resemblance of his Chenopus Syriacus to Natica prcelonga 

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

 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.. 1842. Yoy. Amer. Mend., Ill, Pt. 

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

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

 elatior and fallaz. 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 referred to Tyhstoma. The resemblance 

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



