98 BRACHYPODELLA, JAMAICAN. 



solidated layer of carbonate of lime crystals. While project- 

 ing below, the process does not nearly close the cavity of the 

 whorl. The animal retracts its foot a whorl or two above the 

 process. B. alba minima from Swift River also has a similar 

 process. 



This structure was first noticed by Mr. G. H. Clapp. It 

 differs from the closing plate of Clausilia by being flexible 

 throughout, with a wide attachment instead of a slender 

 peduncle, and probably the two structures are not homolo- 

 gous. Owing to its incoherent texture, this process is, doubt- 

 less, soon lost in dead individuals, from which the soft parts 

 are ordinarily removed by maceration ; but in shells collected 

 alive and dried, it seems to be invariable. I saw no trace of it 

 in B. agnesiana. The other species should be examined with 

 fresh material. 



The name Myckostoma was originally proposed for a series 

 of species now classed as Brachypodella s. sir., but including 

 C. subula Fer., with a reference to Pfeiffer's Monographia, 

 which shows that by "C. subula Fer." a form of C. alba C. B. 

 Ad. was intended. Von Martens subsequently nominated C. 

 subula Fer. as type of Mychostoma, referring to Pfeiffer's 

 subula illustrated in Philippi's Abbildungen, and represent- 

 ing a form of alba. It seems allowable, therefore, to use the 

 name Mychostoma for the Jamaican group of forms related to 

 alba, rather than to restrict it to the real subula of Ferussac, 

 a species the author of Mychostoma did not intend. 



There are two groups of species : that of B. agnesiana, sin- 

 istral forms from the southern watershed of the eastern end 

 of Jamaica, and that of B. alba, dextral, and chiefly from the 

 western end of the island, but occurring in Portland also, in 

 the East. 



44. B. AGNESIANA (C. B. Adams). PI. 2, figs. 13-16. 



Shell sinistral, very long, pillar-shaped, white except where 

 stained by the contained soft parts; lusterless; densely and 

 minutely sculptured with fine, very oblique and slightly 

 curved thread-striae. Whorls nearly flat, the last convex 

 above, then concave, its last half freely projecting in a rather 



