THE NAUTILUS. 43 



Operculum of three whorls, each nearly covered by a white, level 

 lamella arising from the inner margin, spreading nearly to the outer. 



Male: alt. 11.8, diam. 13 mm. 



Female : alt. 12.5 diam. 15 mm. 



El Jique de la Argolla, Barrio de Rio Seco de San Antonio, 15 

 miles northeast of Guant&namo, under stones, Charles T. Ramsden 

 12-24-'! 1. 



The cotypes figured were observed coupling Mar. 19, 1912. 



This species is closely related to A- pseudalatum. It is larger, 

 with more rapidly enlarging whorls, the aperture relatively larger, 

 its diameter more than half that of the shell, while in A. pseudalatum 

 it is less than half; and it differs especially in sculpture, the major 

 axial threads being much more numerous and closer together. 

 Annularia (or Choanopoma) alatum Pfr. is a more opague, solid shell 

 with no sutural channel, coarser, unequal striae, and a differently 

 formed lip. 



In both A. ramsdeni and A- pseudalatum the last whorl is free in 

 front just before finishing the lip, but the additional thin lamina and 

 superior appendage of the lip connect with the preceding whorl in 

 the fully adult stage. This species is named for the discoverer, Mr. 

 Charles T. Ramsden. 



Dr. W. H. Dall has called attention to the fact that the generic 

 name Annularia has precedence over Choanopoma for species of 

 this type. 



ANNULARIA PSEUDALATUM Torre, n. sp. 



The shell is openly umbilicate, wider than high, with a low conic 

 spire; corneous; whorls 3| to 4^, very convex, the last tubular, 

 barely in contact with the preceding at the aperture. Sculpture of 

 straight, slightly retractive and very thin axial threads, separated by 

 intervals in which there are several (three to five) delicate axial 

 striae. There are several weak spiral cords within the umbilicus, the 

 lowest one stronger than the others. The first If whorls are smooth. 

 Aperture oblique, circular, the peristome thin, narrowly expanded, 

 duplicated by a thin outer lamina along the columellar, parietal 

 and upper margins, this lamina expanding in a forwardly concave 

 lobe above. Operculum of about 3 whorls, similar to the preceding 

 species. 



Alt. 7.2, diam. 10.2 mm. 



