100 THE CRAG POLYZOA. 



from which no very certain deductions as to the general habit of the growth can be 

 drawn. 



Finding it impossible to reconcile the characters of either of these species to any 

 hitherto described, I have abstained from any conjectural synonymy, and would only 

 remark that the only species with which it is probable one or other of them may have 

 some relation is Retepora (Hornem) Jlauelliformis of Mieheliu (' Icon. Zoophyt.,' p. 314, 

 pi. Ixxvi, fig. 1). 



2. RAMOSJE. 



Ramis undiquaque se tendentibus, libcris, seu raro ramusculis transversis, distantibus 

 irregulariter coujunctis. ^ 



Branches spreading in all directions, free, or very rarely and irregularly united by 

 transverse ramuscules. 



5. H. HTJMILIS (n. ftp.) PI. XIV, figs. 5, C. 



Polyzoario parvo, erecto ; ramis brevibus, dichotomis, curvatis, insequalibus, e trunco 

 brevi centrali undiquaque surgentibus. Superficic anteriori reticulate sulcata, sulcis 

 porosis ; posteriori sulcis porosis delicatulis ornatfi. Cellularum orificiis orbicularibus, 

 irregulariter dispositis. 



Polyzoarium very minute, consisting of short, dichotomous, curved, unequal branches, 

 diverging on all sides from a short trunk, which is affixed by a circular expanded base ; 

 anterior surface reticulato-snlcate, with pores in the sulci ; mouths of cells orbicular, 

 scattered ; posterior finely sulcate, with rather large puncta in the sulci. 



Habitat. C. Crag, S. Wood; J. S. B. 



This abundant species is at once recognisable by its minute size and peculiar mode 

 of growth, as well as by the regular fine striation of the posterior surface, and more 

 especially of the common trunk and its expanded base. Considerable differences are 

 observable in the minute characters, in some cases almost sufficient to justify the 

 suspicion that more than one species may be included, but upon consideration these 

 differences all appear to be reducible to a common type. The polyzoarium consists of 

 short, cylindrical or subcylindrical, forked branches, springing from a common stem, of 

 considerably greater diameter and expanding gracefully at the base. The celliferous 

 surface is usually the uppermost, but in some instances, as at fig. 5, the openings of the 

 cells seem to be mostly placed on the under side. The posterior or opposite surface is 

 more or less distinctly and regularly sulcate or fluted, the surface being otherwise smooth, 

 and the bottom of the sulci furnished with small rounded pores. 



