ATLANT. DEEP-SEA EXPED. 1910. VOL. III]. 



PTEROPODA. 



55 



The median part of the acetabuliferous appendages 

 consists of a short wall connecting the two lateral arms 

 with each other and carrying 5 peculiar suckers on narrow 

 peduncles (fig. 40), three longer ones alternating with two 

 shorter ones. These five suckers on the median part are 

 very irregular in shape and differ in structure from those 



Fig. 41. Pneumodermopsis macrochira, buccal organs: 

 J. Jaw; H. Hook sacs; R. Radula. 



of the lateral arms (fig. 43—44). They may be protruded 

 so as to have the concave surface of ordinary suckers 

 (fig. 40*) or retracted as in fig. 44, 40**, so as to form 

 a hood-like cover round the end of the peduncle. 



The median lobe of the foot is large and tongue- 

 like, ordinarily wiih a blunt apex (fig. 36 — 37). In one 

 individual however (fig. 38) it was obliquely bent and 

 contracted to a long and narrow point. 



In contracted individuals the wings may be absolutely 

 concealed within a collar-like fold formed by the skin of 

 the body (fig. 37). In the specimen shown in fig. 35 — 36, 

 on the other hand, the soft skin of this part of the body 

 is irregularly expanded, so as to form a series of globe-like 

 protuberances scattered round the base of the wings and 

 foot. Having seen this in only one individual, I cannot 

 tell whether it should be considered a normal pheno- 

 menon. 



A lateral gill is in most of my individuals represented 

 only by a thin and pigmentless spot on the skin of the 



right side of the body. In one specimen, however 

 (fig. 38), this part of the skin protrudes like a small 

 triangular fold. 



The posterior gill consists of four longitudinal ridges, 

 meeting at the posterior end of the body (fig. 35— 36, 38). 

 In contracted individuals this gill is invaginated but even 

 then the four ridges may be seen (fig. 37). 



The skin is in contracted specimens covered with 

 small tubercles except at the right side round the lateral 

 gill. These tubercles are, however, not seen in extended 

 individuals, the skin being here smooth and faintly pig- 

 mented. 



The visceral mass fills the whole body. 



Geographical distribution. This species has 

 been described by Meisenheimer from the southern Indian 

 and Atlantic oceans. 



During the ''Michael Sars" expedition it was taken 

 at no less than 10 stations scattered along the whole 

 route and at various depths (see table). It seems therefore 

 judging from its extended horizontal and vertical distri- 

 bution to be an eurythermal form. 



Pneumodermopsis michaelsarsi n. sp. 



PI. VI, fig: 45—48. 



The single individual of this species, taken by the 

 "Michael Sars" expedition, is shown in fig. 45—46, pi. 

 VI. The proboscis with the whole buccal mass was invagi- 

 nated, and although I have isolated the other buccal 

 organs I did not succeed in loosening the acetabuliferous 

 appendages in toto, so that my description of these organs 

 must be fragmentary. 



Radula (formula 6—1—6): lateral teeth narrow and 

 pointed, with small basal plates, increasing in size towards 

 the median line (textfig. 42). 



Jaw: a cylindrical papilla abruptly truncated above 

 and bordered by a series of small spines (pi. VI, fig. 47, J). 



Hook-sacs: shallow with about 30 short hooks 

 (fig. 47, H). 



Acetabuliferous appendages (fig. 48) carrying 

 suckers of the ordinary type; shape of the appendages 

 and number of the suckers 

 unknown. 



Foot: lateral lobes 

 short and triangular; me- 

 dian lobe narrow, pointed. 



Gills: lateral gill 

 a triangular lobe on the 

 right side of the body, 

 carrying one longitudinal Fig . 42 . Radu i a o[ Pneumodermopsis 

 crest running from the michaelsarsi. 



