ZOOLOGY. M0LLU8CA. 187 



it is almost impossible to determine its exact relationships. 



Chromodoris zebra. (PI. 15, figs. 3, .3a.) 



Animal of the form typical of the genus ; head portion con- 

 siderably extended and expanded in motion ; caudal portion 

 moderately elongated ; base flattened ; mantle beaded im- 

 mediately over the tail. 



Color bright blue above, variously lined and streaked with 

 light yellow; on the dorsal surface the yellow markings are 

 disposed in longitudinal wavy or nearly straight lines, one or 

 more specially prominent lines along the dorso-lateral border. 

 Sides of animal irregularly reticulated or angulated with yel- 

 low markings; under surface- pale blue, bordered with faint 

 yellow. 



Ehinophores deep indigo or black, the rhinophoral aperture 

 bordered with yellow; gills 12 or 13, black, bordered with yel- 

 low, and carrying blue cilia ; under surface of head blue, with 

 yellow spots. 



Length, when expanded, three and a-half inches. 



Three specimens, dredged in about ten fathoms on the north 

 side of Harrington Sound. I dissected one of these and found 

 that the stomach is lodged entirely within the mass of the liver. 

 The alimentary canal is sharply deflected forward (dorsally) 

 beyond the buccal or oesophageal tracts, and is caught up in a 

 nerve ring proceeding from the supra-oesophageal ganglia. 



This species appears to be third or fourth of the genus found 

 in the western Atlantic. It differs clearly from the C.pidurata 

 of Morch ( C Morchii, Bergh, Mus. Godef., part xiv) and C. gonato- 

 phora of Cergh, two West Indian species. In the scheme of color- 

 ing the species appears to be nearest to Doris pulcherrima of Can- 

 traine {Malacologie M^iterranienne, p. 57, PI. 3, fig. 6, — D. 

 Villafraifica? of Risso), from which, however, it differs in a 

 number of details, such as the number of gills, etc. 



Onchidium (OnchidieUa) trans-Atlanticnm. (Fl. 15, figs. 4, 4a.) 



Body convex, smoke color or dark olive ; lighter, dirty or 

 greyish-green on the under surface ; pedal disk considerably 



