120 Proceedings of the Mad. Lit. Society [no. 1, new series, 



by these curious little animals. The second species of which a 

 single individual only was obtained has the shell covered by a strong 

 epidermis the lower edge of which is prolonged into a broad keel 

 serving to sustain the shell in an erect position during the process 

 of swimming. This species is probably new to Science. 



Several specimens of a species of Glaucus, an aberrant group 

 intermediate between Gastropods and Pteropods (although gene- 

 rally included among the former), were taken in Lat. 34 S. These 

 are without shells but are furnished with lateral symmetrical append- 

 ages which are supposed to be bronchise and also serve for pur- 

 poses of locomotion. 



Dr. Traill's specimen differs from the common kind and appears 

 to have been considerably mutilated. It may prove to be new. 



But the richest harvest was obtained in the class of Pteropods. 

 Of the 8 or 9 genera constituting the family of Hyaleidce in this 

 group, numerous specimens were obtained belonging to Hyalea, 

 Cleodora, Cuviera and Creseis or Theca and one species of Limacina. 

 The genus Hyalea was particularly prolific of species. Some it is 

 probable have now been met with for the first time. Their speci- 

 fic characters are carefully pointed out and all are faithfully repre- 

 sented in the drawings. 



Mr. Traill has some excellent remarks on the analogy between the 

 organization of the young of some kinds of Gastropod Molluscs 

 and that of the adult Pteropod, and has observed that the young 

 of the Cyprcea or Cowry shell when first released from the egg or 

 capsule and before they are able to crawl, exhibit a mode of pro- 

 gression very similar to that of the Pteropods. 



The greater part of the specimens described were captured in 

 the night, the habits of most of the genera being more or less cre- 

 puscular or nocturnal, except the genus Creseis which wa3 often 

 met with during the day. 



Dr, Traill's memoir was referred to the Committee of Papers, 

 and will appear in the Journal. 



