PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 309 



I)r. Carpenter, seeing young specimens, could not recognize the pore- 

 tufts of Gould. Shortly before his death, however, he sent me speci- 

 mens which showed them plainly; it is evidently a character in this 

 group of very little importance. 



As regards its identity with vcstita; when dry, the Xew England form 

 precisely resembles the figures from Sowerby\s type-specimen in his 

 Conchological Illustrations, taken from a dried specimen. He consid- 

 ered Erncrsonii a synonym, and I fully agree with him, but have kept 

 the two separated in the foregoing synonymy for the convenience of 

 those who may doubt this. 



This species is very close to A. Pallasii, but is distinguishable by the 

 larger and laterally much more expanded exposed portions of the valves, 

 by its flatter form, and proportionally sparser and longer seta?. When 

 dry, the whole form of the valves is visible in vestita from above, like 

 the bones of a Peruvian mummy; in Pallasii, however, the integument 

 is so much more coriaceous and thick, that in dry specimens hardly any- 

 thing of these outlines is visible. Aliddendorf's figure, copied by 

 Chenu, well represents A. Pallasii when fresh. In cabinets it is rare, 

 and is not common in the field where collectors have searched for it. 



Amicula Pallasii. 



Chilon Pallasii Midd. Bull. Acad. Set St. Petersb. vi, p. 117, 1S47. 



Chiton (subg. Phoenochiton, sect. Diehachiton, subs. Symmetrogejjhy) us) Pallasii 



Midd. Mai. Eoss. i, p. 93, 1847; Sib. Keise, p. 1G3, t. xiii, f. 1-9; t. xiv, f. 



1-6, 1851. 



Amicula Pallasii H. & A. Ad. Geu. i, p. 481, 1854.— Clicnu. i. p. 383, 1859. 

 Stimpsoniella Pallasii Cpr. Bull. Essex lust. 1873, p. 155. 



A. t. valvarum mucrone cordiformi solum externe conspicua; intus 

 v. post, mopaloidea, utr. lat. unifissata. sinu caudali minore. lamina po- 

 stica extus rugosa lato, brevi; v. centr. 1-, v. ant. G-8-fissatis; lam. 

 acutis ex fissuris umbonem tenus sulcatis; lam. sutur. ant. modicis hand 

 separatis, sinu lato brevi ; post, latis, regulariter arcuatis, a sinu postico 

 lato alto separatis, (Cpr.) Limbus (zona) luxurians in pallium extendi- 

 tur, totum animalis dorsum rotundatum obtegens, valvas obvolvens et 

 occultans, solis octo aperturis minutis, rotundatis, in linea mediana, qm- 

 bus aditus ad umbonem valvarum patet ; color squalido lutescens; epi- 

 dermis dorsalis undique versum fasciculis pilorum crinita. Lon. 07, Lat. 

 48, Alt, 21 mm. Div. 120° 



J?a&.— Okhotsk Sea, Midd. ; Pribiloff, Aleutian, and Shumagin Islands, 

 Dall! 3 to 10 fathoms, very rare. Seven specimens examined. 



The rounded back, tough and hairy girdle with minute holes for the 

 tips of the valves, the valves themselves less transverse as a whole and 

 much less exposed than in ccstita, are the characters by which this spe- 

 cies may be readily distinguished from the latter. My specimens have 

 only six fissures in the anterior valve against eight in a specimen of 

 vestita of the same size. 



