OF OONCHOLOGY. 159 



Salpa oymbiola, n. s. 

 Proles aggregata, ignota. 



Proles solitaria. Haemal side boat-shaped, with one median 

 and two nearly lateral non-elevated carinae. Integument of 

 this portion thickened, separated by an impressed line from the 

 dorsal portion, and produced into a short, rather blunt point an- 

 teriorly ; prolonged in a sub-cylindrical long, roundly pointed 

 caudal termination behind. Dorsal portion nearly egg-shaped, 

 resting as if in a boat, on the haemal shield, Oral opening mod- 

 erate, lips slightly thickened. Anal opening inconspicuous, not 

 produced, semilunar, small. Nucleus brown, not prominent ex- 

 ternally. Nervous centre in the anterior dorsal third. A broad 

 transverse muscular band across the middle of the dorsal side, 

 divides on each side into five principal branches. These are sub- 

 divided as follows : The first anterior branch sends one band 

 above and two below the oral opening. These are continuous. 

 The second, third and fourth continue simple and terminate ab- 

 ruptly at or near the lateral carinae of the haemal shield, where 

 a blood vessel passes from one to the other, forming a continu- 

 ous loop around the haemal portion. The fifth bands sends one 

 branch above and another below the efferent aperture, and a 

 third branch terminates abruptly as in the three preceding. 



Length .7. Diameter *3 in. 



Habitat. North Pacific, near the Aleutian Islands, July 21, 

 1866. Lat. 42° 13'. Lon. 145° 45'. Coll. reg. No. 303. Dall. 



This species was obtained in great abundance, always single 

 and free, notwithstanding the appendages before and behind. 

 Proles of aggregated salps, which may have been the immature 

 form of this species, were also abundant. 



LIST OF FIGURES. 



Plate 13. 



1. Dentition of Ocinebra lurida, Midd. 



2. " Amphissa versicolor, Dall. 



3. " Purpura crispata, Chemn. 



4. " Chorus belcheri, Hinds. 



5. " Macron lividus, A. Adams. 



6. " Trochiscus Norrissii, Sby. 



7. " Fissurella volcano, Rve. 



8. " Lucapina crenulata, Sby. ; a, b, uncini ; c, 



two pieces of jaw from below. 



