LIMOPSIS. 161 



tunculina. Gray added, a fifth name (Limnopsis) in 

 1840 ; and Herrmannsen, being apparently misled by 

 Agassiz, considered Limopsis as a synonym of Brown's 

 genus Crenella. The last two errors may be attribut- 

 able, however, to lapsus calami, or to a too hasty attempt 

 at classification. Only a very few species were until 

 lately known in a recent state ; but Mr. A. Adams has 

 given, in the ' Proceedings ' of the Zoological Society 

 for November 1862, a description of no less than nine 

 additional species from different parts of the world. 

 Many species flourished in the tertiary, and others in 

 the cretaceous period. 



4fr 1. LIMOPSIS 



Area aurita, Brocchi, Conch, foss. Subap. ii. p. 485, tav. xi. f. 9. 



BODY cream-colour : mantle thin and plain-edged, open in 

 front and at both sides : gills consisting of two pairs the outer 

 pair being the larger, and overlapping the other which is folded 

 together, with the edges projecting outwards : foot narrow 

 and worm-shaped, when fully extended longer than the shell, 

 bluntly pointed at each end ; it is protruded from the anterior 

 side ; foot-stalk or pedicle short and broad : byssus filmy. 



SHELL roundish-oval, with an oblique outline, compressed, 

 solid, opaque, rather glossy : sculpture, numerous and fine 

 longitudinal striae, which radiate from the beaks to the outer 

 margins, besides equally numerous but irregular concentric 

 ridges, some of which are larger than the rest, and all are 

 more or less beaded or notched by the intersection of the 

 striae ; at the posterior side, these markings are deeper and 

 stronger, and the surface is slightly granulated : colour porce- 

 lain-white : epidermis yellowish-brown, forming in front and 

 at the sides a long fringe, which projects beyond the edge 

 of the shell : margins rounded on all sides except at the back 

 or hinge-area, which is sometimes straight, giving that part 

 the appearance of having an ear-like appendage on each side : 

 beaks small, sharp, and prominent, regularly incurved : hinye- 



* Eared. 



