126 DISCOPHOR^. Part III. 



sacs and another, of a similar length, between them and the ocular lobes, and one 

 short tentacle between the two small lobes of each sac, so that each tentacular 

 pouch sustains five tentacles, three of which are long and two short. The margin 

 of the disk is, therefore, divided into forty-eight lobes, sixteen of which are ocular 

 lobes and thirty-two tentacular lobes, two and two of which are separated by 

 a short tentacle, while there is one large tentacle between the two pairs and 

 another outside of each pair, so that the total number of tentacles, large and small, 

 is forty. As in Placo'is, the central cavity is very wide, and the radiating pouches 

 comparatively short. The disk is flatter than that of Pelagia proper. The type 

 of this genus is Chrysaora lactea Esch. (Acalephs, PL VII. Fi(j. 3), to which must 

 be added the Pelagia quinquecirra Des. 



PoLYBOSTRYCHA Brandt. The general aspect of Chrysaora helvola Br., which I 

 consider as the type of this genus, is so similar to that of the genus Chrysaora 

 proper, that it may well be questioned whether they do not belong to one and 

 the same natural group. In both there are eight tentacular pouches, terminating 

 in two marginal sacs, and forming two distinct marginal lobes, separated by a deep 

 indentation in which there is an eye; and eight tentacular pouches with two 

 distinct lobes, between which and on the sides of which hang the three tentacles 

 characteristic of the tentacular pouches of Chrysaora. However, a closer comparison 

 at once shows differences which are unquestionably structural differences, and there- 

 fore indicate different genera. In the first place, instead of being similar' to one 

 another, there is a marked difference in the outline of the ocular and tentacular 

 pouches. The ocular pouches are widest midway, and narrowest towards the central 

 cavity, and again narrower near the margin; while the tentacular pouches are 

 widest near the margin, and branch off into four sacs, the middle ones forming 

 the tentacular lobes, between which projects one tentacle, while the other two 

 tentacles start from the lateral sacs near the ocular lobes. See the figure of 

 Mertens', in the paper quoted above, PI. XV. Fuj. 4. To this genus Brandt also 

 refers the Chrysaora melanaster, represented in the same paper, Pis. XVI. and 

 XVII. ; this species shows, however, another combination of characters which I 

 consider as generic, and for it I propose the following name: 



Melanaster Ay. Ocular pouches terminating in two distinct sacs, forming broad, 

 distinct lobes, separated by deep-rounded indentations; tentacular pouches termi- 

 nating also in two distinct sacs, forming broad, distinct lobes, between and on the 

 sides of which there are three tentacles, as in Chrysaora and Polybostrycha. But 

 here the tentacular and ocular pouches are similar in structure, as in Chrysaora, 

 and not alternately broader, near the margin and near the main cavity, as in 

 Polybostrycha; they differ, however, from Chrysaora in the great development of 

 these marginal lobes, and in the presence of an auxiliary small lobe between the 



