316 Note on the Oxygyrus and Bellerophon. [April, 



VI. — Note on the Genera Oxygyrus and Bellerophon. By W. H. 



Benson, Esq. B. C. S. 



"When I described the Pelagian genus Oxygyrus in the 4th volume 

 of the Journal, from specimens taken on the surface of the Indian and 

 Southern Atlantic oceans, it did not occur to me to search for cognate 

 genera in any other order than that in which the characters of the 

 animal showed its place to be ; still less did I expect to find any fossil 

 shell allied to it ; but recent consideration of the recorded characters 

 of the fossil genus Bellerophon of Montfort, which was placed by that 

 author among the Polythulamous Cephalopodes , and was subsequently 

 removed by Defrance, on account of the absence of septa, to the 

 neighbourhood of Argonauta among the Monothalamous Octopoda, 

 suggests the opinion that this shell is improperly associated with the 

 Cephalopoda, and that its real station is among the Nucleobranchous 

 Gasteropoda, with Atlanta and Oxygyrus, to the latter of which genera 

 it appears to be intimately related. 



The manner in which the umbilicated species of Bellerophon are 

 convoluted, the acute keel which is observable in some species, and 

 the sinus which indents that keel within the aperture, are characters 

 which denote the affinity of the two genera ; while the prolongation 

 of the lips on either side beyond the umbilicus, and the shelly texture 

 of Bellerophon, contrasted with the absence of any prolongation of 

 the lips, the subcorneous nature of the habitation of Oxygyrus, and 

 the sudden truncation of its partial keel, form sufficiently prominent 

 characters to distinguish them as generic groups. 



That no recent species of Bellerophon has hitherto been discovered, 

 may be possibly owing to the Pelagian habits of the genus, and the 

 paucity of observers of the interesting Oceanic Testacea. Without 

 specimens I am unable to decide on a point on which Rang and 

 Defrance are at issue; the former stating, in his Manuel, that the 

 shell of Bellerophon is thin ; whereas, in the first volume of the 

 Zoological Journal, Defrance contrasts the great thickness of that 

 shell with the thinness of that of Argonauta. Even supposing the 

 latter statement to be correct, weight will not be considered likely to 

 interfere with the Pelagian habits conjecturally attributed to the 

 genus, it being now well ascertained that the ponderous Nautilus 

 Pompilius ascends to the surface of the ocean with as little difficulty 

 as the lightest of the naked Cephalopoda. 



P. S. — In vol. 4, p. 175, there is a misprint in regard to the loca- 

 lity of Oxygyrus. 29° 30' S. lat. should be 39° 30' S. lat. The 



