708 ZOOPHYTES. 



rough at summit. The specimen is an inch in breadth, and half an 

 inch thick, with some of the slender points a line to a line and a half 

 long. 



POLYTREMA MESENTERINA. (Dana.} 



P. kermesina, mesenterina laminis plicate aggregates suberectis compo- 

 sita, margine minute pannoso aut crispo, cettis spar sis poriformibus 

 irregularibus instructo. 



Deep carmine, mesenteriform, consisting of suberect plicately aggre- 

 gated laminse ; the margin minutely ragged or crispate, and fur- 

 nished with a few scattered pores of irregular shape. 



Plate 61, figure 4, natural size ; 4 a, portion enlarged, showing the 

 character of the margin. 



Tutuila, Navigator Islands. Exp. Exp. 



The clump is an inch broad, and half an inch high, and the plate s 

 are about two-thirds of a line thick, with the margin a little thickened 

 and crisped. The pores are without regularity, and but few in num- 

 ber, appearing like punctures resulting from fracture. This species 

 differs so decidedly from the other Polytremse, that it may well form 

 a new genus. Like the above species, it has probably a nearer rela- 

 tion to the sponges than to zoophytes. It has the habit of an Apsen- 

 desia. 



