388 Mr. H. J. Carter on 



of which is imbedded a parasitic isolated polyp — that is, 

 without any stoloniferous connexion with its neighbours, and 

 therefore unlike the Palythoa of the stem, which has a common 

 sclerodermic union. 



Farrea occa, Bk. (Pis. XII. and XIII. figs. 1-11.) 



General form globular, stipitate, thick, shrubby, subsessile; 

 structure originating in a short, round, hollow stem, about 

 half an inch in diameter, which is extended below into an 

 irregular, massive, root-like expansion, and divided above into 

 two diverging branches, which, afterwards becoming subdivided 

 repeatedly, form the head. Branches thick, short, cylin- 

 drical, hollow or tubular throughout, widely diverging at each 

 division, about 5-12ths in. long by the same in diameter 

 between the joints, dichotomously dividing repeatedly, as just 

 stated, and more or less interuniting on the way ; formed of 

 an extremely thin and delicate reticulated wall or skeletal 

 lamina which, in the upper part, is not thicker than the fibre 

 of which it is composed, but rendered denser lower down, 

 that is towards the base, by additional matter of a similar 

 kind, that thus strengthens the support of the superstructure 

 and causes this part to assume a whitish colour. Extremities 

 of the branches open and dilated (PI. XII.). During 

 growth the termination of the branch, which is circular at 

 first, becomes expanded upwards, then elliptical, and, finally, 

 constricted or approximated in the centre, preparatory to 

 division, when the same thing may be repeated and the divi- 

 sions again divided singly ; or one or both branches may 

 unite with their neighbours respectively, when the result is a 

 single tube that again divides dichotomously ; and so on, till 

 the whole head becomes formed of a series of short-jointed, 

 hollow, dividing and interuniting branches, which thus gives 

 rise to a clathrous structure of a globular form, as above 

 stated. (The "branch" will hereafter be called "tubo- 

 branch.") Consistence firm, elastic. Colour translucent 

 white. Pores in the dermal reticulation (PI. XIII. fig. 11). 

 Vents cloacal or general, i. e. consisting of the open ends of 

 the tubo-branches, into which the smaller ones of the wall or 

 sponge-tissue empty themselves. Surface of the tubo-branch 

 outside uniformly even, covered by the pore-structure. Wall 

 or skeletal lamina consisting of a cylindrical layer of reticu- 

 lated, strong, glass-like fibre, in which the interstices are more 

 or less quadrangular and oblong, the longest diameter being 

 in the direction of the tubo-branch (PI. XIII. fig. 1, ctaaa), 

 and the points of intersection marked on each side by a long, 

 curved, spiniferous process or spur, which is directed upwards 



