BRYOZOA. 395 



Family FENESTELLID.E King. 



Zoaria forming reticulate expansions, celluliferous on one side 

 only, composed of rigid branches united to each other by 

 regular non-poriferous bars called dissepiments; or they may 

 lt j sinuous and anastomose; or even remain free. Primitive por- 

 tion of zoupcia of oblong quadrate or hexagonal outline. Su- 

 perior hemiseptum usually present, the inferior one less fre- 

 quently. Primitive aperture semi-elliptical, being truncated at 

 the posterior side. Superficial apertures rounded, with peris- 

 tome, and. in the perfect state, closed by centrally perforated 

 opercula. 



FE.VESTELLA Lonsdale. Zoaria flabellate to infundibuliform, 

 poriferous on the inside (always?); branches nearly straight, 

 and connected with each other at rhythmical intervals by non- 

 poriferous dissepiments. Zooecia in two rows, separated by a 

 more or less developed median keel. 



Accepted type: F. plebeia, McCoy. Range, Cincinnati to Per- 

 mian. 



SEMICOSCIXIUM Prout, (Carinopora Nicholson) Zoaria funnel- 

 shaped, poriferous on the outer side. Dissepiments wide, very 

 short, the branches appearing on the non-poriferous side to 

 anastomose. Here, also, the fenestrules are sub-rhomboidal or 

 rounded. Zo<ecia in two ranges. Median keel very high and 

 more or less expanded at the summit. 



Type: S. rhomboideum Prout. Range, Niagara to Hamilton. 



FENESTRAPORA Hall. In all respects like Semicoscinium, ex- 

 cepting that the reverse of the zoariurn and the expanded sum- 

 mits of the carinse bear large pores or pits. 



Type: F. biperforata Hall. Range, Upper Helderberg and 

 Hamilton. 



ISOTRYPA Hall (emended). Zoaria infundibuliform; branches 

 connected by dissepiments. Keel at first very thin, then 

 abruptly expanded; at intervals corresponding to the true dis- 

 sepiments, the thickened summits are connected by strong pro- 



3g 8, giving to the superstructure an appearance very much 

 like that of the reverse faee of the frond. Zocecia in two ranges. 



Type: /. conjunctiva Hall. Range, Niagara to Hamilton. 



