ORDER IV 



CRYPTOSTOMATA 



341 



Fenedella Lonsd. (Fenestrella d'OrJj. ; Actinostoina Young) (Fig. 498). Zoaria 

 Habellate or funnel-shaped, poriferous on the inner side. Branches connected at 

 regular intervals by dissepiments. Zooccia in two rows, separated by a plain or 

 tuberciilose median keel. Silurian to Permian. 



Semicoscinium Front {Carino23ora Nich. ; C'ry2:)topora "Sich.; Cycloporina Simpson). 

 (Fig. 499, e). Zoaria funnel-shaped, poriferous on the outer side. Dissepiments 

 wide, very short, the branches appearing to anastomose on the non -poriferous face, 

 where the fenestrules are sub-rhomboiilal or rounded. Zooecia in two ranges, median 

 keel very liigh and expanded at the summit. Silurian and Devonian. 



Fenestrapora Hall. Like the preceding, except that the reverse of the zoarium 

 and the expanded summits of the carinae bear large, scattered pores, or pits. 

 Devonian. 



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#>%Wfl 







» W f*"** imm «.«• ^ 



Pio. 499. 





(I, Archimedes distansVh-. l/i. h, Polypora simnlatrix Vlr. i/i and S/i- c, Hi'.mitrypa prontana Vh: i>/i. 

 d, Unitrypa acaiiUs Hall. ti/i. e, Semicosctnium interruptum H. and S. "/i. /, Fenestralia compacta Ulr. "/] 

 (after Ulricli, Hall, and Simpson). 



Helicopora Claypole ; Isotrypa, Loculipora, Unitrypa Hall (Fig. 499, d). Silurian 

 and Devonian. 



Hemitrypa Phill. (Fig. 499, c). Differs from Fenestella in having a reticulated 

 superstructure, whose meshes correspond in position and number with the zooecial 

 apertures in the branches beneath. Silurian to Lower Carboniferous'. 



Archimedes Lesueur (Fig. 499, «.). Distinguished from Helicopora liy its solid 

 central axis. As a rule, the fenestrated expansion is broken away, leaving only the 

 screw-like axis. Lower' Carboniferous. 



Lyropora Hall. Zoaria flabellate, the fenestrated portion spread between the 

 arms of a non-celluliferous U- or V-shaped support ; free or pedunculate at the base. 

 ZocEcia in from two to five rows. Lower Carboniferous. 



Fenestralia (Prout Fig. 499, /). Having a median keel as in Fenestella^ but with 

 four ranges of zooecia instead of two. Lower Carboniferous (St. Louis Group). 



Polypora M'Coy {Protoretepora Koninck) (Fig. 499, b). Differs from Fenestella 

 in having two to eight rows of cells on a branch, and in wanting a median keel. 

 The latter is sometimes represented by a row of strong tubercles. Silurian to 

 Permian. 



Tlucm.niscns King. Like Pohjptora, Ijut branches Infurcating more freely, and with 

 only a few disse^jiments or none. Silurian to Permian. 



Phyllopora King. Zoaria funnel-shaped, celluliferous on the outer side, and con- 



