316 ZOOLOGY. 



which has been applied to it : the body is stout, broad, 

 oblong and flattened, (but is capable of being volun- 

 tarily shortened, and converted into a nearly globular 

 form,) and terminates in a slender caudal appendage, 

 which bears a very close resemblance to the tail of a 

 lizard. Each side of the body is furnished with three 

 stout branchial members, or fins, placed equidistant 

 from each other, palmated at their extremities, and 

 supplied with numerous short and tapered tentacles, 

 resembling toes. The head is round and conspicuous, 

 and provided on each side with two papillae or tuber- 

 cles, one superior and one inferior, which can be ex- 

 tended in the form of short slender tentacles, like the 

 horns of a snail. The mouth is small, orbicular, and 

 margined with a strong horny structure. An elevated 

 fleshy fold on the neck forms a partial hood over the 

 head. 



The colour of the entire upper surface of the body is 

 dark-blue, with the exception of a broad silvery streak, 

 extending from the head to the extremity of the tail ; 

 the inferior surface of the body and fins is pearl-white. 

 The head also is white, but has a vertical blue line on 

 its centre. The entire animal is enclosed in a tough, 

 but smooth and delicate integument. 



These creatures obtain in greatest number where 

 currents most prevail ; they are active and very preda- 

 tory in their habits, and would appear, from the obser- 

 vations of my brother, which I have already mentioned 

 and confirmed, to subsist chiefly upon the soft parts of 

 the defenceless genera, Velella and Porpita. The speci- 

 mens we captured and kept in sea-water, contorted 

 their bodies into many convulsive attitudes, but seldom 

 employed their branchial fins, and floated buoyantly 

 while passive. When immersed in fresh water they 



