263 



[Genus ENTOCONCHA, J. Miiller, 1852. 



Shell obovate, smooth ; spire short, very obtuse, apex not 

 elevated, whorls rapidly increasing ; aperture transverse, semi- 

 lunar, angulated above, rounded below, width almost equaling 

 the height, margins disunited, the columellar margin straight. 

 Operculum non-spiral. E. MIRABILIS, Miiller. 



Found parasitic in Sinapta digitata, one of the Holothuriidae, 

 at Trieste. A larval mollusk, sometimes referred to the present 

 group, but now placed, doubtfully, with the Nudibranchiata]. 



Genus EUCHRYSALIS, Laube, 1866. 



Small, thin, pupoid, attenuated at its extremities; whorls 

 numerous, short, smooth, suture shallow ; aperture long, narrow, 

 the lip sharp and thin, columella terminated by an indication of 

 a siphon. Silurian Cretaceous; Europe, India. 



Subgenus MITCHELLTA, de Koninck, 1877. 

 Shell elongated, cylindrical-conic, many whorled ; aperture 

 long, extremely narrow, sinuous, attenuated at its extremities, 

 rostrated and prolonged but not canaliculated in front ; peris- 

 tome continuous, the lips subparallel, outer lip reflected ; surface 

 spirally striated. Devonian, Australia. The type is sinistral. 



Genus MACROCHEILUS, Phillips, 1841. 



Shell thick, imperforate, ventricose, aperture effuse below, 

 outer lip thin, columella callous, slightly tortuous and plicate in 

 front. 



Devonian Carboniferous. M. SCHLOTHEIMII, d'Arch. (Struct, 

 and Syst. Conch., t. 68, f. 91). 



The synonym}' includes Polyphemopsis, Portlock ; Plectostylus, 

 Conrad ; Macrochilina and Duncania, Bayle, 1879. 



Subgenus PASITHEA, Lea (Restricted), 1833. , 



Spire short, last whorl ventricose. Rather more slender and 

 cylindrical than the typical Macrocheilus. M. CLAIBORNENSIS, 

 Lea. Eocene ; Alabama. 



Genus BOURGUETIA, Desh., 1871. 



Shell large, turreted ; spire long, pointed ; whorls convex, spi- 

 rally striated or grooved, last whorl large ; mouth oval, angular 

 behind, widened and rounded below. B. STRiATA,Sowb., Jurassic. 



