HETEROPODA 



13 



This species agrees on systematically important points 

 very well with the description given by Vayssiere (1904) 

 of his P. (Firola) hippocampus, so well indeed, that I do 

 not hesitate to identify the two forms, although a few 

 particulars remain doubtful. The concordance with P. hippo- 

 campus is evident with regard to the size and shape of 

 the nucleus, the position and surroundings of the osphra- 

 dium (not mentioned by Vayssiere), the shape of tail and 

 tail fin, and also with regard to the structure of the radula. 



The shape of the eyes, however, has not been con- 

 sidered by Vayssiere ; nor does he mention any difference 

 between males and females with regard to the cuticular 

 spines of the fore-head, and finally the position of the 

 fin in front of the middle point of the body, at stated by 

 Vayssiere, was not to be found in the specimens at my 

 disposal. 



The 24 individuals of Eupterotrachea hippocampus 

 brought home by the "Michael Sars" Expedition all coin- 

 cide with regard to the characters mentioned above. 

 They represent, however, with regard to the structure of 

 their cutis two different varieties. One of these, var. punc- 

 tata, is characterized by presence of numerous cuticular 

 spots (c. sp.) on the ventral side, larger ones along the 

 base of the swimming fin (fig. 34 a), and smaller ones 

 along the cuticular folds of the fore-trunk. Also on the 

 proboscis (fig. 29), and not only on the ventral side, nu- 

 merous small cuticular spots are to be found. In speci- 

 mens belonging to the other variety, var. apunctata, no 

 cuticular spots are to be found (fig. 35 — 37). 



Of the 24 individuals 21 were taken in the Eastern 

 Atlantic, between the African coast and the Azores, while 

 3 individuals were taken at a station in the Western At- 

 lantic. 



Locality 



Depth 

 metres 



Date 

 1910 



Number of 

 individuals 



Size 



St. 



Lat.N. Long.W. 



mm. 





Var. apunctata: 











45 



28° 42' 20" <y 



150 



May 28-29 



1 S 



70 



52 



31-24' 34° 47' 



50 



June 6-7 



1 ¥ 



20 



i) 



— — 







— 



4 S 



40—55 



» 



— — 







— 



4 J 



40—55 



53 



34° 59' 33° 1' 

 Var. punctata: 



1300 



» 8-9 



1 (def.) 



ca. 40 



47 



29° 2' 22° 53' 







May 30 



1 a" (def.) 



? 



48 



28° 54' 24° 14' 







„ 31 



5 S 



45—77 



„ 



— — 







— 



2o* 



70 



49 



29° 8' 25° 16' 



130 



June 1 



Id" 



42 



n 



— — 



180 



— 



1 S 



55 



67 



40° 17' 59° 39' 



100 



„ 27 



2d" 



40—45 



D 



— — 



100 



— 



1 ¥ 



45 



Eupterotrachea minuta, n. sp. 



(PI. IV, fig. 47-52). 



Eyes (fig. 48, textfig. A, 4a) cylindrical in their 

 distal part, but with retinal plates broader than the dia- 

 meter of the cylindrical part. 



Nucleus spindle-shaped, slightly rising above the 

 dorsal level of the trunk (fig. 51, textfig. A, 4 b). Its 

 height is about four times its greatest width. 



The cutis is soft and quite smooth, with the ex- 

 ception of a few cuticular spots round the base of 

 swimming fin, and also on the ventral surface in front 

 of this place (fig. 49). 



The osphradium (o) has a position somewhat to the 

 left of the median plane of the animal, and is surrounded 

 by a wall without tubercles (fig. 51). The right side of 

 this wall forms the median dorsal line, while the left side 

 of the wall is found lower down on the side of the animal. 



Gills, 11 in number, forming a very regular row 

 with no great difference in their length, the largest gills 

 being found on the left side of the animal. 



Tail without tubercles along the muscle bands, but 

 with dorsal and ventral cuticular ridges, the first of which 

 is continued backwards upon the tail fin. The latter is, 

 in the one individual at my disposal, somewhat torn so 

 that its shape can not be accurately described. 



The radula (textfig. B, 4 a— b). Number of rows 

 of teeth unknown. The median plate with 5 — 6 spines 

 on each side of the middle spine, which is not so far 

 protruding as in E. hippocampus (cfr. textfig. B, 3and4). 

 Intermediate plates with a secondary spine at their 

 free ends. Lateral plates nearly as long as the inter- 

 mediate plates. 



Buccal teeth 5 — 6, cone-shaped with a narrow base 

 (fig. 50). 



Only one small individual of this species is at my 

 disposal, and without making sections I am unable to 

 determine whether it is mature or not: I therefore prefer 

 to leave this question open until more material may be 

 obtained. The individual is a male carrying a penis 

 consisting of three small leaves, and a glandular organ, 

 ending in a sucker-like plate (fig. 52). 



Size, 47 mm. in length. 



This species differs from the others in the collection, 

 and from all other species hitherto accurately described, 

 especially in the shape of the eyes and nucleus, which 

 form an intermediate stage between the broad-based eyes 

 and broadly oval nucleus (subgen. Euryops of Tesch) on 

 one hand, and the cylindrical eyes and spindle-shaped 

 nucleus (subgen. Pterotrachea s. s. of Tesch) on the other. 



