56 



KR. BONNEVIE. 



[REP. OF THE "MICHAEL SARS" NORTH 



free angle of the lobe obliquely towards its base; posterior 

 gill consists of four longitudinal crests converging towards 

 a small globular tubercle at the posterior end of the body. 



Skin faintly pigmented. The visceral mass fills 

 the whole body except the narrow tapering part carrying 

 the posterior gill. 



Pneumodermopsis michaelsarsli is distinguished from 

 the earlier known species of this genus in having a 

 posterior gill, while it differs from P. macrochira in the 

 shape of the posterior and lateral gills and of the jaw. 



Locality: Station 42 (23° 2' N., 14° 17' W.). 

 Date: 23 / 5 — 2 Vs. 

 Depth: 250 metres. 



Pneumoderma Cuvier. 



Radula of the family type; median tooth which 

 is wanting in the adult, may be present in the young. 



Jaw of the family type. 



Hook-sacs tube-shaped, with short hooks not 

 essentially longer at the bottom of the sac than near the 

 opening. 



Acetabuliferous appendages: a pair of lateral 

 arms, free or coalescent with the proboscis. 



Pneumoderma atlantica n. 



PI. VI, fig. 49-51. 



sp, 



A 



Ah 





wm 





m 



O-.i- 





%& 



L-C- 





Fig. 43. Pneumoderma atlantica. A. Part of the genital gland; 

 B — C. Contents of the gland (more highly magnified). 



Spongiobranchaea d'Orbigny. 



Radula and jaw of the family type; median tooth 

 present. 



Hook-sacs oviform, with curved hooks varying in 

 length, all reaching the opening of the invaginated sac. 



Acetabuliferous appendages consisting of a pair 

 of lateral arms. 



This genus is not represented in the "Michael Sars" 

 collections. 



My description of this interesting species is 

 based upon one small individual about 3 mm. in 

 length taken by the "Michael Sars" at Station 62. 

 In shape it was so peculiar (see fig. 49—50) as 

 to be almost unrecognisable. 



As will be seen from the figures, the anterior 

 and posterior parts of the body formed an angle 

 with each other, and from the top of this angle 

 a big sphere protruded. 



Opening the sphere I found it to be hollow 

 and to contain a peculiar body formed like a 

 mushroom (fig. 49); the disc of this body was 

 carried upon a narrow peduncle connecting its 

 underside with the body-surface and apparently 

 continuing into the body. 



The disc itself was composed of a great 



number of small cones (textfig. 43 A), rounded 



at the top and mutually connected at the bottom. 



The contents of the cones are figured in textfig. 43, 



B-C, and prove that the organ is a hermaphroditic 



genital gland with ^eggs and spermatozoa in 



various stages of development. The shape of 



this gland, and the arrangement of its contents, 



are typical of gymnosomatous pteropods, and it 



seems necessary to conclude therefore, that the 



gland really belongs to the animal to which it is fixed, 



and that the peduncle connecting it with the body-wall 



is the genital duct. 



An arrangement like this, with the genital gland lying, 

 as it were, outside the body, seems so strange and unique 

 in the animal kingdom, that the most careful examination 

 will be necessary before acknowledging it as a normal 

 phenomenon. Until the connection between this gland 

 and the internal organs of the body has been accurately 

 determined the question as to the meaning of the struc- 

 tures found in Pneumoderma atlantica cannot be con- 

 sidered as definitely settled. I hope to discuss this 

 question in a later paper, and shall here merely draw 

 attention to the fact that an analogous structure has been 



