North American HelicidcB. 87 



se deroule par uiie spire plus large que ceux qui le precedent. Les 

 tours do spire au nonibre de sept sont convexcs, couvcrts de strios fines, 

 rcg'ulieres, rapprocliccs, plus profondes sur le cote superieur que dans la 

 partie ombilicale : ellcs s'attenuent insensiblcment en passant du dessus 

 a la circonference et de la circonference au-dessous. L'ouverture est 

 tres oblique, le bord droit, epaissi en dedans, est renverse en dehors ; il 

 se continue par ses extremites en un bord gauche, sur le milieu duquel 

 se releve une petite dent oblique et courbee que Ton voit tout entiere 

 en dehors lorsque Ton regarde l'ouverture de profil, Cette coquille est 

 d'un blanc grisatre, et elle est ornee de flammules longitudinales, etroites, 

 irregulierement distribuees et d'un brun pale et rougeatre. 

 "Elle a 10 mill, de diametre et 4 de hauteur."* 



Pfeiffer (Mem. i. p. 409, 1848) assigns IL microdontoj to the 

 Bermudas and Texas, " teste coll. Menkeana." 



Muhlfeldt and Desliayes did not know the localities from 

 which their specimens came — the figure and description of the 

 former author are unsatisfactorj^, and the latter described from 

 a single individual, and gives a figure wliich is by no means 

 conclusive. Under such circumstances, considering that the 

 species of the group to which H. cereolus and H. onicrodonta 

 belong are very variable, it is not surj^rising that difficulty 

 should be now experienced in determining them. 



"When in Bermuda, in 1852, I collected a large number 

 of specimens of a finely striated shell, pretty closely agreeing 

 with the description of II. microdonta Desk. / but Mr. 

 Shuttleworth, in 1855, was disposed to think it distinct, and 

 proposed to call it H. delitescensy under w^hich name it has 

 been extensively distributed, but nothing published about it. 



In 1853, Mr. S. sent me specimens labelled " H. microdonta 

 Desh., Key West, Florida," which difter very much from the 

 Bermuda shell, having sharp and more distant striae, and 

 an internal lamella. I also received from the same source 

 examples of II volvoxis Parr., from Ilopeton, Ga. Both these 



* See facsimile of the figure to which Deshayes refers, in W. G. Binney's Supp. 

 to the Terr. Moll., pi. 78, fig. 23. 



