48 CRYPTOCHITON. 



by a deep posterior sinus reaching the external knob ; (3) in the 

 long hairs of the bunches which are disposed in regular pores along 

 the margin and across the sutures, as well as irregularly over the 

 surface." 



MiddendorfFhad never seen specimens of amiculatus, his informa- 

 tion being derived wholly from Pallas' description and figures. 



Dall has given Carpenter's description in his paper on the Chitons 

 of the north-west coast (Proc. U. S. Nat. Mus. 1878, p. 310), and 

 proposes the name Chlamydochiton for the species, on account of its 

 ambient gills. See also under Cryptochiton stelleri. 



Subfamily Cryptochitonin^. 



Genus CRYPTOCHITON Middendorfr& Gray, 1847. 



Cryptochiton Midd,, Bulletin de la Classe Phys.-math. de I'Acad. 

 des Sci. de St. Petersb. vii, no. 8, p. 116 (separate copies distributed 

 in Spring of 1847) ; Beitriige zur einer Malacozoologia Rossica, i, 

 p. 33. — Cryptochiton Gray, Ann. Mag. Nat. Hist, xx, pp. 70, 134 

 (July and August, 1847) ; P. Z. S. Lond. 1847, pp. 65, 69, 169. 



Valves entirely concealed in the leathery girdle, and lacking 

 tegmentum ; their posterior margins produced backward in a deep 

 lobe on each side, the lobes united across the median line, causing 

 the apices of all valves to be removed inward from the posterior 

 edge. Slits subobsolete or lacking in the intermediate valves. 

 Girdle covered with minute tufts of short bristles. Gills extending 

 the entire length of the foot. 



This genus differs from Amieula, and from all other known 

 Chitons, in the union of the posterior lobes of the valves across the 

 median line, causing the apices of the median and anterior valves to 

 be placed subcentrally or at the posterior third, instead of at the 

 posterior margin. 



C. STELLERI Middendorff. PI. 7, figs. 7-13 ; pi. 6, fig. 6. 



Oblong, rather depressed, the bilobed posterior outlines of the 

 valves (in dry specimens) showing through the leathery integument, 

 which completely covers the valves. Color a dull ferruginous or 

 brick-red, very well preserved specimens being rendered much 

 brighter by the closely placed fascicles of brilliant vermilion spines. 



