INVERTEBRATE PALAEONTOLOGY. 4i>7 



own N. hevigatus, published in 1846* (nol bis N. lavigatus, 1840), is synony- 

 mous with it ; also the Indian N. sphtsricus and N. Obignyanus, Forbes, and a 

 Chilian form referred l>y Professor Forbes to JY. lavigatus. Mr. Blanford, 



however, considers both of the Indian shells merely varieties of N. Bouchardi- 

 anus, d'Orbigny, and entirely distinct from N. Dekayi, Morton. I have not 

 the necessary specimens at hand to express any decided opinion in regard to 

 the Indian shells figured by Mr. Blanford all belonging to the one species 

 ^\. Bouchardianus ; but I can fully concur with him in the. opinion that they 

 are certainly distinct from N. Dekayi, Morton. The latter differs, as stated 

 by Mr. Blanford, in having its umbilicus always filled with a solid shelly kind 

 of columella, formed by the thickening of the lip at its connection with the 

 body of the shell on each side, instead of being perforated. N. Dekayi also 

 has its aperture constantly more transverse, and its siphuncle always nearer 

 the inner side, as may be seen by our figure 1, a, plate 27, which represents 

 very nearly the typical form of the species, as I know from a direct compari- 

 son with Dr. Morton's type-specimen, now in the Museum of the Academy 

 of Natural Sciences at Philadelphia; from which type-specimen the fore- 

 going outline-cut showing the position of the siphuncle was drawn. 



It is true that Dr. Morton also referred doubtfully to N. Dekayi, under 

 the provisional name N. perlatus, a more compressed form from Alabama, 

 that would doubtless agree more nearly in the outline of its aperture, and in 

 several other respects, with some of the Indian forms, as well as with the 

 Chilian N. Orbignyanus, Forbes. I have not seen specimens of the Alabama 

 shell showing the position of its siphuncle, but I very much doubt its identity 

 (judging from its form only) with N. Dekayi proper, as I have seen no ten- 

 dency among our specimens (that do not differ also in the position of the 

 siphuncle) to assume this more compressed form. 



Dr. Ernest Favre, in his "Moll. Foss. Craie des Env. de Lemberg," 

 refers to N. Dekayi a shell that is evidently quite decidedly distinct ; while 

 he also cites in the synonymy forms not only distinct from Dr. Morton's 

 species, but not identical with the species he figures, which has a more 

 dilated aperture than N. Dekayi, while it shows little ribs on the inner volu- 



* His figures of this shell given in the Voyage of the Astrolabe, agree very closely in form, as 

 well as in the outline of the aperture and the position of the siphuncle, with N. Dikayi ; but as they 

 were drawn from au internal cast ouly, we have not the means of knowing certainly whether or not the 

 small umbilical perforation seen in the cast was entirely filled with a solid columella-like callosity on 

 ca' h side, as in Morton's species. If it has this character, it may be identical with that form. 



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