MARINE POLYZOA. 51 



of the marginal cells of a large sessile, well-formed avicularium. 

 The frond attains a height of several inches, having linear trun- 

 cate segments, slightly dilated towards the end, of a red-brown 

 colour, generally with one or two dark spots. It appears to be 

 very abundant in Algoa Bay. 



In Krauss' ' Zooph. d. Siids.' p. 35, a new species of Flustra, 

 or rather of Carbasea, is described under the name of Flustra 

 marginata, of which figures are also given, minutely and highly 

 finished. In general habit, and in the front view of the cells, 

 there is not the slightest resemblance between this form and Car- 

 basea armata ; but what is given as the back view of the cell, in 

 Krauss' figure very curiously, bears a striking resemblance to 

 the front view in C. armata ; and although, in the description of 

 his species, Krauss takes no notice of the lateral avicularia, they 

 are very clearly represented in this figure. It might therefore be 

 supposed that Krauss has confounded two distinct species under 

 his F. marginata. 



4. CARBASEA CRIBRIFORMIS. PL LXVIII. fig. 1. 



Cells oval, irregularly disposed. Frond reticulated. Ovicells 

 cucullate, immersed. 



Retepora cornea, Busk, Voy. of Rattlesn. i. 380. 

 Hab. Off Cumberland Island, 27 fathoms. 



The peculiar reticulated frond of this species is so different 

 from that of any other of its congeners, as at once to distinguish 

 it. This form shows very strikingly how artificial some of the 

 generic distinctions in this class of Polyzoa are ; for, except in the 

 flexible, horny consistence of the frond, there is no distinction 

 between C. reticulata and a Retepore. 



/3. Aperture occupying only part of the front of the cell. 



5. CARBASEA DISSIMILIS. PI. L. figs. 4, 5, 6, 7- 



Cells pyriform, much attenuated below. Aperture oval, 

 anterior. Marginal cells with an acute, short, spinous process 

 above on the outer side. A sessile projecting avicularium in front 

 of each cell below the aperture. 



F. carbasea, var. /3., Lamk. Ann. s. V. ii. 221. ii. 2d ed. 

 Hab. Tasmania, Hooker. 



This species indicates the transition between the Flustradse 

 and Cellulariadae. In the form especially of the outer cells, and 

 in the presence of anterior avicularia upon most of them, it re- 

 sembles Menipea. The continuous polyzoary however, and the 

 frondose habit, are sufficient to indicate its true position. 



D 2 



