32 AMERICAN JOURNAL 



B. [Liriola.) 



Shell thin, horny ; smooth, or furnished with fine radiating 

 lines, which do not interrupt the margin. Apex marginal or 

 submarginal, twisted to the left of the median line in most of 

 the species. The gill passes behind the heart and lung. The 

 jaw is simple and arcuate. The rhachidian tooth is moderate, 

 with a simple pointed cusp. The inner laterals are long, narrow 

 and strongly bidentate. The outer laterals are broad and tri- 

 dentate with short cusps. 



This section is typified by >S'. thersites, Cpr., and would in- 

 clude jS. lateralis, Gld., S. redemiculum, Rve., S. 3Iacgillivrayi, 

 Rve., S. Lessoni, Blainv., and all the similar species, such as 8. 

 tristensis, S. Uneolata and others from the South American 

 coast. The species are more numerous in the temperate zone, 

 though not confined to it. 



If it be considered desirable to give a name to this group, 

 Liriola might be used in a restricted sense to indicate it. 



The following species belongs to the first section : 



SnPHONARIA ALTERNATA, Say. 



Patella alternata, Say, Journ. Phil. Acad. Sci. vol. v, p. 



215, Feb., 18-26. 

 Siphonaria alternata, Say, Am. Conch, part iv, pi. 38, 1832. 



Binney's Say's Works, pp. 124, 192, pi. 38. Binney L. 



and F. W. Shells of N. Am. part ii, p. 153, fig. 254. 



Chenu, 50, pi. xiii, fig. 3. 



Shell conical, with more or less elevated, unequal ribs, thirty 

 or more in number. Apex subcentral, recurved obliquely, the 

 tip pointing in a nearly parallel direction with the longitudinal 

 axis of the shell, and acute. Color brown, radiated with white; 

 base oval. Length three-tenths of an inch. 



Say's figure of this species in Binney's reprint is represented 

 as with too few ribs and too smooth interspaces. The wood-cut 

 copy in the L. and F. W. Shells of N. A. is also very poor. 



The external appearance of the animal is much like the next 

 species. The mantle edge is brown, thick and somewhat corru- 

 gated. The remainder is livid slate color. The lobe which 

 closes the pulmonary opening is large and thin, gray and edged 

 with brown. There were no eyes visible, yet they probably exist 

 and are very minute. The anatomy resembles that of the next 

 species, except that the penis is larger in proportion to the size 

 of the animal. 



The jaw is simple and arcuated. The central tooth is very 

 slender ; the cusp has a simple point. The inner laterals have a 



