REPORT ON THE PTEROPODA. 
empty shells, obtained from deep-sea deposits, the surface is perfectly smooth, and the 
shell is then clear and translucent, with a brownish-grey colour. This makes me think 
that the reticulation of the surface is confined to the epidermis. 
II. The reason for the numerous titles applied to the present species is that the 
specimens have been studied in very different conditions. 
Hitherto only one author has studied the living Pteropod in its adult state, namely 
Costa, who described it as Spinalis recurvirostra. 
The two oldest descriptions of this species, that of d’Orbigny (under the title Atlanta 
reticulata ) and that of Souleyet (under the title Spirialis clathrata), refer to young- 
individuals. This is clearly shown from their smaller size (2|- mm.), the fewer turns in 
the spiral (three), the incompletely developed columellar rostrum, and the well-developed 
reticulation towards the aperture. 
As to this reticulation, I have noticed that in the single specimen obtained on the 
Challenger Expedition, which was at the same stage as that observed by d’Orbigny and 
Souleyet, the markings are hexagonal, and not tetragonal as one might suppose with low- 
power examination. 
Finally, the empty shells- from deep-sea deposits, which have lost their superficial 
reticulation and brown colour, have been described by Forbes. Jeffreys (1871), and 
Fischer (1882) 1 under the specific title physoides. 
Habitat. — Pacific Ocean, 20° S., 87 3 W. (d’Orbigny) ; perhaps in the Atlantic, at the 
Canaries (Krohn) f Mediterranean, Naples, during the day, at a depth of 100 metres 
or more. 
The empty shells of this species have been dredged at various points in the 
Mediterranean ; in the deep-sea dredgings of the “ Travailleur ” (Fischer) ; on the 
coast of Algiers (“Porcupine” Expedition, 1870, Station 51, 36° 55' N., 1° 10' E.) ; 
off Crete (Jeffreys), 1 2 3 in the AEgean Sea (Forbes), and finally in the North Atlantic 
(“Valorous” Expedition). 4 
Challenger Specimens. — I. Living. 
Between Stations 264 and 265, August 24, 1875; on the route from the Sandwich 
Islands to Tahiti; lat. 13° 15' N., long. 152° 2' W. 
This single specimen was stained and mounted in balsam. In order to examine the 
reticulation of the shell and the form of the fins, I had to extract the specimen from the 
balsam, and in this operation the shell was broken. 
II. Deposit shells. 
Station 23, March 15, 1873 ; off Sombrero Island; lat. 18° 24' N., long. 63° 28' W.; 
depth, 450 fathoms ; bottom, Pteropod ooze. 
1 Comptes rendus, vol. xciv. p. 1201. 
2 Beitrage zur Entwickelungsgeschiclite der Pteropoden und Heteropoden, p. 43. 
3 Ann. and Mag. Nat. Hist., ser. 5, vol. xi. p. 401. 4 Ann. and Mag. N at. Hist., ser. 4, vol. xix. p. 337. 
