﻿April, 1857.] 



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His names will probably be retained, all of them, except Sar- 

 siadae, being, however, strictly attributable to Eschscholtz. 



Gegenbaur (Joe. cit. p. 218,) divides these Medusae, which he calls 

 Craspedota, from the presence of the vail, into seven families. 

 They are Oceanidae, Thaumantiadas, Aequoridae, Eucopidae, Tra- 

 chynemidae, GeryonidaB, and Aeginidae. These divisions are 

 founded on collective structure, so that the characters employed 

 by Gegenbaur, are drawn from all the principal organs of these 

 animals. The author also makes mention of the larva-type, as a 

 subsidiary character in his diagnoses of the families. His Oce- 

 anidae include the Oceanidae, Sarsiadae, and Willsiadae of Forbes, 

 with other genera, which he thus divides into sub-families : 

 Oceanidae, proper, with short digestive trunk, simple tentacula, 



and simple radiate-tubes. 

 Sarsiadae, with simple tentacula, simple radiate-tubes, and very 



much elongated digestive trunk. 

 Bougainvillidae, with short digestive trunk, oral tentacula, and sim- 

 ple marginal tentacula grouped in bunches. 

 Willsiadae, with branching radiate tubes and simple tentacula. 

 Cladonemidae, with forked radiate tubes and branched tentacula. 



These groups appear to me natural, but of unequal value ; thus 

 setting aside the fact, that the development of Willsia is not known, 

 (and otherwise its proximity to Cladonema seems quite plausible,) 

 the Bougainvillidae are distinguished from all the rest by the pres- 

 ence of highly organized oral tentacula, and the grouping into 

 bunches of their marginal tentacula, while so far as known, their 

 larvae are allies of Eudendrium and Tubularia. On the other hand 

 Oceanidae and Sarsiadae agree in having Corynidae for their larvae, 

 no oral tentacula, and their marginal tentacula, though frequently 

 complicated in structure, never exhibiting that peculiar grouping 

 characteristic of Bougainvillidae. Again, Gegenbaur separates the 

 Thaumantiadas from the Eucopidae, placing Aeginidae between 

 them. The genus iEquorea, on account of its large, broad-mouthed 

 digestive cavity imbedded in the disk, is certainly more distantly 

 related to either Thaumantiadae or Eucopidae than these are to 

 each other, when we consider that the greatest distinction between 

 them consists in the fact, that Thaumantias has ocelli and not mar- 

 ginal sense capsules, while the reverse is the case with Eucope. 

 But Agassiz' genus Tiaropsis is certainly a Thaumantiad, and yet 

 its larva is Campanularia, which is also true of Eucope. These 

 two groups, therefore, are no further removed from each other 

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