﻿148 



PROCEEDINGS OF THE 



[April, 1857. 



gether, are still of frequent occurrence and indicate the structural 

 tendencies of the group. Thus the tentacula exhibit a marked 

 tendency to specialization, both in number, grouping, and form. 

 Ocelli are frequently wanting. There are also found in one 

 part of the group, oral tentacula, which, like the marginal tentac- 

 ula, in another part of the group, are branched. The radiate 

 tubes also are sometimes branched. 



The group, with these general characters, contains three minor 

 groups, quite distinct from each other. They are Pennaridee, Tu- 

 bularidee proper, and Hippocrenidaa, and are characterized as 

 follows : 



i. pennaridjE. mihi. 



The general range of form in this group (which must eventu- 

 ally be subdivided) is like that in the group of Sarsiadas. We 

 must, however, except the genus Willsia, which with Chrysomi- 

 tra, is remarkable among Endostomata for the shortness of its ver- 

 tical in comparison to its horizontal diameter. In the other gen- 

 era, the bell is deep, the transverse diameter short, the digestive 

 trunk more or less elongate, and Sarsioid in form. The mouth is 

 simple, or provided with bunches of thread-cells, like that of the 

 young in Oceanidse. The radiate tubes are in two instances 

 branched ; the tentacula vary, but the present group is the only 

 one in which they are found branched. In all the genera here 

 included, except Cladonema, there are no ocelli, and the exterior 

 of the disk is ornamented with lines of thread-cells, or pigment 

 cells, ascending from the bell-margin. 



The Larvas have two whorls of tentacula, of which the oral 

 whorl are clavate at the tip like those of the very young larva of 

 Tubularia proper. The body, also, of this larva is not expanded 

 into a broad basal enlargement at the insertion of the whorl of 

 lower or filiform tentacula, as in Tubularia when full grown, but 

 the whole body preserves the cylindrical form of the same 

 part in the young stage of Tubularia, at the moment when it 

 becomes fixed. The genus Stauridium has but eight tentacula in 

 all, and might be regarded perhaps as a connecting link between 

 the Tubularidae and Corynidae; at any rate, notwithstanding its 

 correspondence in character with Pennaria, when its medusas are 

 better known, Stauridium will probably form a new group.* 



* Prof. Agassiz has mentioned to me his having found in Charleston harbor a 

 Stauridioid genus, but I have not met with it. 



