161 



Figure. 



Lyonsia striata. PL 41. Fig. 222. Shell, showing its convex form, 

 striated surface, and truncated posterior end. 



Genus 6. ANATINA, Lamarck. 



Animal; with the mantle closed except for the passage of afoot, 

 which is sometimes small, sometimes broad and compressed ; 

 siphons long, either slender and separated, or united and en- 

 closed in a wrinkled epidermic sheath. 



Shell ; oblong, inequilateral, nearly equivalve, thin, ventricose, 

 gaping ; hinge composed of a spoon-shaped process in each 

 valve, containing the ligament, with sometimes two central 

 teeth in front of each. 



Under genus Anatina 1 include two well-marked forms represented by 

 the genera Periploma and Anatinella. The Anatina proper, so far as 

 the animals are known, have rather lengthened siphons united together 

 within a wrinkled epidermic sheath after the manner of Mya and Panopaa ; 

 their shell is of very light transparent silvery-white substance, inflated and 

 ventricose, and mostly produced behind into a pouted beak. In A. pra- 

 temcis {Cochlodesma, Courthouy; Periploma, Schumacher) the spoon- 

 shaped process is more distinctly ovate and prominent, and the animal is 

 said to have its siphons divided in their whole extent. In A. Candida 

 {Anatinella, Sowerby), of which the animal is not known, the spoon-shaped 

 process is more conspicuous still, and there are two cardinal or central 

 teeth in front of it in each valve. These differences may prove hereafter 

 to afford good distinguishing characters for genera, but the group needs 

 to be investigated and monographed. Several fine species are known in 

 collections without names. The following are all that have been described. 

 One species only, A. pratemds, is British, the rest are from the seas of 

 Japan, India, and the Philippine Islands, New Zealand, and North and 

 South America. 



Species. 



1. alta, C. B. Adams. 5. elegans, PMl. 9. lanterna, JBom. 



2. angulifera, Phil. 6. globulosa, Lam. 10. Leana, Conr. 



3. anserifera, Speng. 7. imperfecta, id. 11. lenticularis, Sow. 



4. argentaria, Conr. 8. insequivalis, Sc/ium. 12. papyracea, Say. 



