Chap. II. CTENOPIIOR.E EURYSTOM^. 191 



since these Acaleplis are among the most dehcate known, and so frail that it is 

 utterly impossible to preserve them for any length of time, in alcohol or any other 

 fluid. Direct comparisons of species inhabiting distant regions are therefore out of 

 the question; and all that can be done in attempting to arrange them systemati- 

 cally is to infer their true characteristics and affinities from the scanty information 

 furnished by various authors. Milne-Edwards justly remarks, that, m the present 

 state of our knowledge, it would be difficult to point out any real differences 

 between the Beroe of the Mediterranean and those observed in the Antilles, in 

 the northern Atlantic, about the Cape of Good Hope, and in the South Seas. As 

 I have had frequent opportunities of examining two very different American species 

 of this type, I feel in a measure prepared to call attention to the characteristic 

 features of these animals. 



As Milne-Edwards has already shown, the Beroids proper are not broadly open 

 at both ends ; and there is only one free communication with their main cavity, at 

 the actinal pole. The opening mentioned by Cuvier, Delle Chiaje, and Lesson as 

 existmg at the opposite pole, is either an illusion resulting from the inversion of 

 the abactinal end of the spherosome, or the result of an accidental perforation of 

 that region. The form of the body varies greatly in different states of contraction; 

 but under all its changing aspects, it is easy to perceive that the characteristic 

 form is that of a compressed egg, truncated at one end, at which the mouth is 

 situated. The chief differences among extreme forms consist in the greater or less 

 extension of the actinal axi.s, in the more or less tapering of the abactinal or of 

 the actinal pole, the blunter or the narrower end of the body being at opposite 

 poles in different species, and in the compression of the lateral sjiheromeres. The 

 prominence of the abactinal ends of the lateral spheromeres, while the anterior and 

 posterior spheromeres may be depressed in the direction of the circumscribed area, 

 constitutes another element of the differences noticed in the form of these animals. 

 In all the representatives of this sub-order the oral opening is truncate, with the 

 sole exception of Lesson's Idya dentata, from the western coast of Africa, which 

 is represented from a sketch hj Bang (Acal. PI. II. F/'j. 3) as deeply indented 

 between the rows of locomotive flappers, and having a tentacle projecting from 

 the angle of each indentation. If this is really so, and not the result of lacei-ation, 

 this species should be considered as the type of a distinct genus, forming a distinct 

 family. The circumstance that Lesson was indebted to Bang for the drawing he 

 published, strongly favors the supposition that we have here the first indication 

 of a distinct genus, forming by itself a family of the Ctenophorte Eurystomce, distinct 

 from the Beroids proper. For this genus I would propose the name of Eangia, 

 in memory of the distinguished author of important contributions to the natural 

 history of the Ctenophorse, and call the family Bangiid.e. 



