PLEUROBRANCHUS AGASSIZII MAC FARLAND 63 



obtain, the two ganglia being united into a single flattened mass, 

 circular in outline, and having a diameter of 0.36 mm. The 

 pedal ganglia are slightly smaller than the cerebro-pleural ones, 

 being 0.3 mm. in diameter, and having the same flattened, 

 spherical form. The eyes are very large, nearly spherical struc- 

 tures, 0.15 mm. in diameter, and borne upon very short optic 

 nerves. 



Connectives. The cerebro-pedal and pleuro-pedal connectives 

 (PI. XII, fig. 55, c. p. con., pi. p. con.} are extremely short and can 

 only be seen after carefully dissecting away the capsule and dis- 

 placing the ganglia by gentle pressure upon the cover glass. 



Otocysts. The otocysts, not represented in fig. 55 of PI. XII, 

 are spherical structures, 0.06 mm. in diameter. They are situated 

 at the upper inner border of the inner face of the pedal ganglia, 

 close to the cerebro-pedal connectives, and contain a large num- 

 ber of minute otoconia. 



REPRODUCTIVE SYSTEM. 



The glans penis is extruded in all three specimens. It is 

 short and bluntly conical, and is surrounded at its base by a con- 

 spicuous fold of integument, which is continuous all around save 

 at the posterior side, where its ends overlap with a deep fissure 

 between them. Just within this fissure, and close to the posterior 

 portion of the base of the glans penis is the female opening (PI. 

 XI, fig. 54, v). The exact relations of this opening with that 

 of the duct of the nidamental-albumen gland could not be made 

 out satisfactorily. They are very close together, the gland duct 

 seeming to have a common external opening with the vagina, 

 but the condition of the material made this and other points in 

 the structure of the reproductive system uncertain. In sections 

 the glans penis is circular, and there is no indication of an 

 anterior wing-like appendage, such as is given by Vayssiere as a 

 characteristic of his subgenus Pleurobranchus s. str. (Monog. 

 '98, P. 307). 



SYSTEMATIC POSITION. 



There can be no doubt but that this species is distinct from 

 the three Antillean forms described by Morch ('63), especially 

 in the light of the careful anatomical description which Bergh 



