256 MYRIOZOID.E. 



elevated avicularium ; mamillae scattered here and there 

 over the zoarium, bearing large avicularia, with a 

 slender, pointed mandible. Oaecia rounded, broader 

 than long, somewhat flattened in front, the base enve- 

 loped by a thick layer, which incloses a semicircular 

 space, traversed by radiating lines. 



Colonies forming rather large, irregular crusts ; the cells 

 sometimes disposed in detached series (forma laxa, 

 Smitt). 



Form eschariformis (A. W. Waters). Zoarium erect and 

 foliaceous. 



RANGE OF VARIATION. Smitt has described as a new 

 species, under the name of Hippothoa divergens, a Floridan 

 form which, I confess, seems to me to be identical with 

 S. biaperta. The only distinction between them, so far 

 as his descriptions enable me to judge, of any importance, 

 is a slight difference in the form of the mouth. In 

 Michelin's species (= Hippothoa biaperta, Smitt) the 

 sinus appears to be smaller, and to partake more of the 

 character of a notch in the centre of the lower margin. 

 In the divergens form, to which all the British specimens 

 which I have seen are referable, the suborbicular orifice is 

 produced below into an open, wedge-shaped sinus, the 

 peristome usually slants gradually away to the bottom of 

 it, and there is only a slight constriction of the aperture 

 on each side. But there are many intermediate varia- 

 tions ; and remembering the diversities in this particular 

 that are met with in such a species as S. auriculata, it 

 is difficult to regard this difference as possessing any 

 great importance. The shape and general character of 

 the cell, and the structure and position of the lateral 

 avicularia, are, I believe, the same in both forms. In 

 both, the mamilUe, supporting large avicularia with a 

 pointed mandible, are present, and often in considerable 

 numbers. 



