IDMONEIDJL 90 



4. H. RHIPIS (a. sp.} PI. XIV, fig. 4. 



Polyzoario explanato, flabelliforrai ; t ramis subcylindricis, contiguis ; fenestris parvis 

 irregularibus. Cellularum orificiis in seriebus transversis plerumque dispositis, integris 

 seu infra emarginatis, subovatis, prominulis, pcristomate tenui expanse circimidatis. 

 Superficie anteriori poris raris, distantibua ornata ; posteriori granulosa, delicatule sulcata, 

 poros miuimos, distantes subinde ostendente. 



Polyzoarium expanded, flabelliform, simple; branches subcylindrical, closely con- 

 tiguous ; fenestrse small, irregular ; mouths of cells disposed in irregular transverse rows, 

 entire or emarginate below, suboval, margin prominent, thin, expanding ; anterior surface 

 punctate, puncta rare, distant ; dorsal finely granular, finely sulcate, without pores, or 

 with very few minute ones. 



Habitat. (f Crag, S. Wood; J. S.B. 



This species can only be confounded with H. canaliculata, from which, however, it is 

 undoubtedly distinct. The more striking features by which they may be distinguished 

 are : 



1. In general aspect the polyzoary in //. canaliculata is constituted of far larger or 

 wider branches, which are further apart and connected by fewer transverse ramules than 

 in H. rhipis. 



2. The dorsal surface of the branches in H. canaliculata is remarkably flattened or 

 almost concave, deeply and coarsely scored by bifurcating, irregular sulci, which are 

 furnished with large, tolerably frequent, elongated pores, whilst in H. rhipis the dorsal 

 surface is not so flat, and almost even or marked with fine shallow sulci, which very rarely 

 exhibit here and there a minute perforation. 



3. A striking difference is observable in the condition of the mouths of the cells, which 

 in H. canaliculata are disposed irregularly, or in some parts pretty regularly, in quincuncial 

 order, depressed and usually emarginate above, in which direction they are continuous as 

 it were, with a shallow ascending channel, whence the specific name ; whilst in H. rhipis 

 the mouths of the cells are placed with tolerable regularity in transverse rows, are entire 

 or continuous all round with a thin, somewhat expanded border, which is contracted 

 below sometimes almost into a sort of narrow spout, the intermediate surface being 

 irregularly punctured. 



Another character, apparently distinctive of the two, may also be found, though with 

 more difficulty, in the circumstance that the walls of the tubes in H. canaliculata are 

 closely perforated with minute puncta, which, so far as I can perceive, are wanting, or at 

 any rate far less numerous, in the tubes of H. rhipis, in which species it is also to be 

 remarked that the tubes themselves are much less than in H. canaliculata. 



With respect to the general aspect of the two, or any characters that can be thence 

 drawn, little can be said, for //. canaliculata has hitherto occurred only in broken fragments, 



