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



HETEROPODA 



11 



occurring on the sides of the fore-trunk in a number of 

 species of Pterotrachea. 



There is, however, a well-marked difference between 

 these structures: the cutis-shield of P. (Heterodens) 

 gegenbauri forms a thick, elastic, gelatinous mantle, 

 covering the back and sides of the whole fore-trunk, 

 making the latter appear broadly pearshaped, while the 

 soft neck folds in other species hang down ventrally. 

 and thus affect very little the appearance of the body as 

 seen from the dorsal side. 



Generally no cuticular spots are found in this 

 species, the cuticle being quite clear and transparent all 

 over the body. In one specimen, however, a few cuticular 

 spots were found on one side (the left) near the base of 

 the swimming fin. 



Clear conical tubercles are irregulary scattered all 

 over the dorsal side of the trunk, and in two longitudinal 

 rows on each side of the cuticular shield, while the 

 cuticle of the ventral side is quite smooth. Such is the 

 case also with the cuticle of the probocis. 



The distribution of tubercles on the tail and round 

 the osphradium has been described above; there remains 

 now only to be mentioned a double row of tubercles 

 (fig. 45) on both sides of the seminal duct in the male. 



The penis (fig. 45) forms a very conspicuous organ 

 on the right side of the male. Its copulatory part is 

 formed by an S-shaped double leaf, while the glandular 

 part is finger-shaped, clear and transparent and containing 

 near its free end an oval brown body. 



This species is represented by 10 specimens taken 

 off the African coast and near the Azores. 



Locality 



Depth 

 metres 



Date 

 1910 



Number of 

 individuals 



Size 



St. 



Lat. N. 



Long. W. 



mm. 



23 



35° 32' 



7° 7' 



1215 



May 5-6 



1 



65 



n 



— 



— 



200 



— 



1 



45 



25 



45° 46' 



8° 16' 



1700 



„ 7-8 



1 



45 



28 



36° 0' 



7° 19' 



450—200 



9 



1 



? 



34 



28° 52' 



14° 16' 



200 



. 13-14 



2 



f80 

 \70 



42 



28° 2' 



14° 17' 



150 



„ 23-34 



2 



(65 



175 

 80 



56 



36° 53' 



29° 47' 



150 



June 10-11 



1 



58 



37° 37, 



29° 25' 



300 



. 12-13 



1 



40 



Among other species probably or possibly belonging 

 to the subgenus Heterodens, may be mentioned: Ptero- 

 trachea scutata, Gegenbaur (1885), with its shield-like 

 cuticular swelling on the fore-trunk, an P. (Firola) talis- 

 mani, Vayssiere (1902), which carries peribuccal teeth 

 like P. Gegenbauri. A further investigation of these two 

 species will, however, be necessary in order to decide 

 whether they correspond also in regard to other characters. 



Subgenus II, Eupterotrachea, includes the species of 

 Pterotrachea without a cutis-shield, without peribuccal 

 teeth, and with the pedal ganglion above the anterior 

 edge of the swimming fin. 



Eupterotrachea hippocampus, Vayssiere. 

 (PI. Ill, fig. 28—39). 



Eyes (figs. 29, 36 a, textfig. A, 2— 3 a) broad based, 

 so that the diameter of the retina is somewhat like the 

 height of the whole eye. 



The nucleus (figs. 30, 38, textfig. A, 2—3 b) is short 

 and broad (its width about one-half of its length), and 

 does not reach the dorsal level of the body. 



The cutis is soft and smooth, in fixed specimens 

 hanging down as folds on both sides of the neck. - 

 Tubercles are found scattered along the lateral muscle 

 bands of the tail, and occasionally also on the osphradium 

 wall. Cuticular spines before the eyes are found in two 

 irregular groups in the females (Sp. fig. 36 a and b), 

 while in the males they are either lacking or rudimentary 

 (figs. 28, 37). As to the existence of cuticular spots in 

 one variety of this species, see below. 



Osphradium (o.) in the median dorsal line sur- 

 rounded by a cuticular wall, smooth or with scattered 

 tubercles (figs. 30, 38). 



Gills short, 12—15 in number, forming a row po- 

 sterior to the osphradium wall (figs. 30, 38). 



The longitudinal muscles of the tail are weak, the 

 dorsal and ventral ones are covered with cuticular ridges 

 without tubercles figs. 33, 38, 39). The dorsal ridge is 

 continued backwards upon the tail fin; the latter is there- 

 fore not leaf-like, as is the case with the species described 

 above, but shows a triangular cross-section, (figs. 33, 39). 



The radula (textfig. B, 2 — 3) shows about 23 rows 

 of teeth. The median plate with a far protruding 

 median spine and more than five small spines on each 

 side. Intermediate plate without a secondary spine at 

 its free end, although it may be present as a rudiment in 

 one variety of the species (textfig. B, 3). Lateral plates 

 nearly as long as the intermediate ones. 



Buccal teeth (fig. 31) broad-based, 5 — 6 in each of 

 two rows in the palate. 



The copulatory part of the penis (fig. 32) consists 

 of a pair of broad, leaf-like lobes, while its glandular 

 organ is finger-shaped, with a sucker-like extension at the 

 end, and about twice as long as the two leaves. 



In the females a broad, rounded cuticular papilla 

 is found on the right side of the animal in front of 

 the nucleus (fig. 30, P). 



The size of the individuals of this species varies 

 from 20 — 80 mm. in length, most of the full-grown 

 specimens measuring 70 — 80 mm. 



