NO. 1863. }fOLLU8K8 OF THE GENUS ALVANIA—BARTSCH. 347 



the base; parietal wall covered with a thick callus which renders the 

 peritreme complete. 



Doctor Carpenter's tj^pe (Cat. No. 12217, U.S.N.M.) comes from 

 Cape San Lucas, Lower California. It has 4 post-nuclear whorls 

 and measures: Length 2.7 mm., diameter 1.1 mm. 



ALVANIA PERLATA Morch. 



Alvania perlata Morch, Mai. Blatt., vol. 7, 1868, p. 68. 



Shell small, solid, elongate-ovate, marked by a peripheral chestnut 

 band which is apparent upon all the whorls of the spire. Nuclear 

 whorls smooth. Postnuclear whorls marked between the sutures 

 by four spiral cords, the spaces between which are not crossed by 

 the contmuations of the axial ribs. Aperture small, subcircular; 

 outer lip somewhat constricted and expanded anteriorly. 



Morch's type, which is in the Copenhagen Museum, came from 

 Central America. It has 6 post-nuclear whorls and measures; 

 length 2.8 mm., diameter 1.5 mm. 



ALVANIA GALAPAGENSIS, new species. 



Plate 30, fig. 9. 



Shell ovate, yellowish white. Nuclear whorls at least two (having 

 their surface eroded in all our specimens). Post-nuclear whorls 

 flattened in the middle, marked by rather slender, irregularly slanting 

 axial ribs, pf which 18 occur upon the second and third, and 20 upon 

 the penultimate turn. The ribs are less than one-third as wide as 

 the spaces that separate them. In addition to the axial ribs, the 

 whorls are marked by poorly developed, spiral cords, of which 3 

 occur upon the second and third, the first being at the summit and 

 the second marking the termination of the anterior third between 

 the sutures, while the third is halfway between this and the suture. 

 The mtersections of the axial ribs and spiral cords form the merest 

 indications of nodules, while the spaces inclosed between them are 

 squarish pits on the second and third whorls, and also between the 

 first and second cords on the penultimate whorl. The space between 

 the second and third cords on the penultimate whorl is divided by a 

 slender, spiral thread wliich renders the pits elongate, with their 

 long axes parallel to the spiral sculpture. Suture slightly constricted, 

 showing the jDOsterior edge of the first basal cord. Periphery of the 

 last whorl marked by a sulcus as wide as that separating the first 

 and second spiral cords between the sutures and, like it, crossed by 

 the feeble continuations of the axial ribs, which terminate at its 

 posterior border. Base produced anteriorly, slightly rounded, with a 

 faint suggestion of concavity in its middle, marked by six spiral cords, 

 which grow successively weaker and closer spaced from the periphery 

 to the umbilical region. Aperture subcircular; outer lip very thick, 



