TESCH— PTEROPODA AND HETEROPODA 181 



Pterotrachea placenta Lesson* is probably the same as this species, as the author 

 emphasizes the fact of the tail having " ni nageoire a sa pointef, ni chapelet a sa suite " ; 

 moreover the animal is described to be " d'aspect tuberculeux." Lesson found a specimen, 

 of a length of 50 mm., off the coast of New Guinea. 



Notwithstanding some difference in the shape of the fin and the position of the 

 sucker, I suppose Cardiapoda pedunculata d'Orbignyj is also to be classed with the 

 species under discussion, as no appendages at the tail have been recorded. d'Orbigny's 

 specimens (length 30 — 40 mm.) wer*e taken in the tropical Atlantic Ocean. 



Pterotracheidse. 



Pterotrachea Forskal. 

 Subgenus Pterotrachea s. s. Tesch. 



15. Pterotrachea (s. s.) sp. 



Stat, kk (1), Desroches Atoll, Amirante Group. 



It is impossible for me to determine this species with any certainty, as the only 

 specimen is a female, and so the relative size of the sucker at the fin cannot be measured. 



The animal has a total length of 33 mm., of which the proboscis measures 6 mm., the 

 tail 8 mm. ; the maximum breadth of the fin is 5 mm. There are no spines before the 

 eyes. At the left side of the visceral nucleus, which is slender and pointed as in all 

 species of this subgenus, four gills, two of which are very inconspicuous, are to be seen. 



The middle plate of the radula bears a central cusp, which is rather long, pointed and 

 very slender ; at either side follow five or six shorter ones, somewhat curved inwards. On 

 the dorsal roof of the buccal cavity two longitudinal muscular folds, leading into the 

 oesophagus, show some chitinous teeth, five at either side, the proximal ones being very 

 small. 



I have not ventured to name this specimen, which, though beyond doubt belonging 

 to the above named subgenus, does not exhibit any characteristic feature. To give it 

 a name would only serve to increase the already great confusion in the nomenclature 

 of the Pterotrachea species. 



16. Pterotrachea (s. s.) microptera \ Tesch. 



Stat, a (1), Mauritius ; k (t), Nazareth Bank. 



Both specimens were females ; the determination to my regret therefore cannot be 

 regarded as quite certain. They were of nearly the same size, the first specimen of 

 a total length of 21 mm., the second, in which the tail and also the fin are torn awav, 

 of 23 mm. The proboscis in both measures 6 mm., and is slender and pointed. In the 

 first specmien the fin is extremely small, its maximum diameter being only 2 mm. It is 

 mainly on account of this small fin that I have referred the specimens, which in general 

 aspect are very much alike, to the species mentioned above. The skin is without any 



* Voyage de la " Coquille," Zoologie, T. ii. p. 253, PI. in. fig. 2. 



t From this we may conclude that Souleyet and also E. A. Smith were wrong in identifying their 

 species with that of Lesson. 



\ Voyage dans V Amiriqut meridionale, T. v. p. 15G, PI. XI. fig. 5. 



