332 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



spongiosis; simi miiiore, lainiuato, lamiua atroqiie latere et iuterduin 

 iu medio flssata; zona squamulis peri^arvis, solidioribus, irregulariter 

 instructis Itevibus, iustructa; braucliiis fere ambieutibus, per valvas 

 VI posticus contiuiiis. Lon. 40, Lat. 26 mm. Div. 135°. 



jlah. — Sitka, Port Etches, 9-18 fms., gravel, rare; south to Puget 

 Souud. Six specimens examined. 



This rare and fine species is not i^articularly handsome, being of dull 

 and livid colors, but is peculiarly characterized by the straight trans- 

 ^•erse ribs on the dorsal areas, with spongy interspaces, and by the 

 pretty regular division of the lateral areas into three well-marked radi- 

 ating costre, which are separated in the insertion-plate by two fissures. 

 IsTo other species of the region resembles this in sculpture. Muzzle with 

 a pectinated margin in front j)roduced into rounded lappets at the 

 corners. Gill-rows as long as the foot, containing each 28-35 branchine. 

 Veil absent. Mantle-edge plain, narrow. There is a small spherical 

 lump on each side of the girdle just behind the posterior ends of the 

 gill-rows, which are turned out toward the girdle and widely separated 

 behind. The anus is large, median, and crenate, opening on the upper 

 part of the hinder end of the foot. I^o ovarian openings could be 

 detected, and the species presents some peculiarities which call for 

 fiu'ther research with more material. 



Subgenus Lepidopleurus s. s. Cpr. 



Lepidopleunis Mertensii. 



Chiton Mertensii Midd. Ball. Ac. Sci. St. Petersb. vi, p. 118, 1846. 



Chiton (PhwnoGhiton, Ramachiton, Stenosemus) Mertensii Midd. Mai. Ross. p. 34, 



125, pi. xiv, f. 1-3 a-h, 1847. 

 Leptochiton Mertensii H. & A. Adams, Gen. Rec. Moll, i, p. 473, 1854. 



L. t. colore rubido, interdum intensiore nebuloso; mucrone subcen- 

 trali, hand elevatoj intus v. term. 9-12-, centr. 1 fiss.; dent, acutis; sub- 

 grundis majoribus; sinu lato, planato, hievi; zona rubida sen pallidiore, 

 squamis ovoideis, nitentibus, lievibus vix regulariter confertissime im- 

 bricata. Lon. 20, Lat. 6 mm. Div. lOOo. 



Hah. — Sitka and vicinity, south to Monterey, Cal. Many specimens 

 examined. 



Middendorf 's description and figures of this shell do not agree well 

 together. Its fine red color, sliarx) and prominent sculpture, usually 

 free from erosion or nullipore, and beautifully shiniug-and regular scales, 

 render this one of the most attractive and easil}" recognized of the 

 Alaskan Chitons, There are no others in that region hkely to be con- 

 founded with it. It rarely shows a white valve or a dash of white on 

 some of the valves. 



The Soft parts of this species are whitish. The anus is on a papilla. 

 Mantle-edge narrow, grauulose, forming on each side behind the last 

 branchia a rounded lump or tumor. Near this the ovarian openings 

 were thought to be detected. Muzzle semicircular, cornered behind on 



