OF CONCHOLOGY. 135 



ISNORADSIA TRIFIDA, Cpr., n. S. 



This new and beautiful species was obtained at Sitka in 14 

 fathoms stony mud, off the fish-house. It will be described by 

 Dr. Carpenter, who has made a special study of the Chitons. 



ONCHIDIIDiE. 



ONCHIDELLA, Gray. 



Onchidblla borealis, n. s. 



Animal small, black with dots and streaks of yellowish white, 

 foot light-colored, also muzzle and tentacles. Back regularly 

 rounded, but a little pointed in the middle ; smooth or very 

 finely granulose, tough and coriaceous. Eyes globular, blue, on 

 very short constricted tentacles. Muzzle short, rounded-trans- 

 verse. Head not produced beyond the anterior edge of the 

 mantle. Sexual appendages on the right side, near the head. 

 Foot ovate, narrow, rather roundly pointed behind. Lon. -3 in. 



Habitat, Sitka, Alaska Territory, on the rocks near tide marks, 

 especially on the small islets in the Bay. Dall, August, 1866. 



LIMNiEID^E. 



LlMNiEA Palmbri, n. s. 



Shell, large, moderately thick, solid, of a rufous tint; rather 

 polished outside, sculptured with incised lines visible without a 

 lens and more crowded on the edges of the whorls than on their 

 more convex portions ; suture deeply canaliculated, whorls much 

 inflated, four ? in number (apex decollated), columella thin, very 

 slightly reflected, furnished with a small but very evident plica- 

 tion, umbilical fissure nearly covered by the reflected columella ; 

 outer lip roundly arched, not reflected or thickened ; aperture 

 rounded ovate, less than half as long as the shell ; last whorl 

 much the largest, but not rapidly enlarging. Length of the last 

 two whorls -86 in. in total length, probably about an inch, great- 

 est width of last whorl -58 in. 



Habitat, Taqui River, near Guaymas, Mexico, emptying into 

 the Gulf of California. Collected by Dr. Edward Palmer. 



I know of no species with which this can fairly be compared; 

 indeed, had the case been otherwise, I should not have felt justi- 

 fied in describing it as new, from a single decollated specimen. 

 It will be referred with propriety to the section Bulimncea, Hald. 

 The incised lines, very round whorls, and deeply channelled 

 suture, are its distinguishing characters, and it has a slight 



