NO. 2283. NEW PACIFIC COAST CHITONS— DALL. 503 



ISCHNOCHITON MARMORATUS, new species. 



Chiton small, elegantly marbled with white, gray, and brown, with 

 a velvety girdle covered with mottled gray, white, and brown densely 

 set spinules; anterior valve with about 12 radial rows of prominent 

 pustules, the rows sometimes bifid, and the ground microscopically 

 decussate; slits 8-10; posterior valve smaller, with 8-9 slits, the 

 mucro slightly behind the center with a peripheral irregularly double 

 row of pustules while the central area is coarsely axially reticulate; 

 intermediate valves with one slit, hardly mucronate, the jugal and 

 pleural tracts axially sculptured with beaded threads finer on the 

 jugum; lateral areas with two or three radial rows of prominent 

 pustules which near the girdle project like little cylinders in an ir- 

 regular manner; interior whitish, with hardly perceptible jugal 

 sinuses and very narrow sutural laminae. Length, 7; width, 4; 

 height, 1.5 mm. 



Habitat. — Pacific Grove, Monterey Bay, California; Mrs. Blood. 

 Oat. No. 218735, U.S.N.M. 



Eemarkable for its unusually projecting pustular sculpture. Chi- 

 ton marraoratus Gmelin, belongs to another genus. 



ISCHNOCHITON BRYANTI, new speciea. 



Chiton of moderate size, flattish, with dorsal keels, a girdle with 

 oval smooth small imbricating scales mottled with light and dark 

 brown, the valves light olivaceous brown with blackish flecks ; anter- 

 ior valve less than semicircular, with about 13 rather irregular, some- 

 times bifurcate, thread-like beaded radial riblets, the whole surface 

 covered by a microscopic reticulation; internally there are 13-14 

 slits, the insertion plates radiately striated ; posterior margins dentic- 

 ulate, the jugal sinus shallow and small ; posterior valve smaller, the 

 general sculpture on the posterior area like that of the anterior 

 valve, internally with 11 slits, the sinus shallow, the sutural laminae 

 narrow, the insertion plates striated; intermediate valves axially 

 short, slightly mucronate, keeled; the jugal area minutely decus- 

 sate; j)leural tracts with 8-10 prominent axial threads and 6-8 finer 

 transverse threads in the interspaces, the whole valve covered with 

 the minute decussation; lateral areas with two strong radial minutely 

 nodulous ribs bifurcate distally, the posterior rib annulate, denticu- 

 lating the margin ; internally whitish, with a shallow jugal sinus and 

 one slit in each end. Tjcngth, 9; width, 5.5; height, 2 mm. 



Habitat.—'' California,"^ F. W. Bryant. Cat. No. 253826, U.S.N.M. 



This species has the gill rows ambient, and the striated insertion 

 plates are peculiar. It came to the United States National Museum 

 with the Bryant collection and without any more definite locality 

 than that above given, but most of his shells were from the southern 

 part of the State. 



