492 R. M. Brydone — New Cretaceous Polyzoa. 



rocks from the south, over newer. The fossils yielded by the 

 mudstones in the borehole are few in number, but such as can be 

 identified suggest a low Wenlock Shale horizon for the deeper beds. 

 If the core believed by Professor Garwood to be Longmyndian is 

 correctly identified, the Upper Llandovery Sandstones of the Corton 

 ridge rest directly upon a nucleus of Pre- Cambrian rocks. 



II. — Notes on new and imperfectly known Cretaceous Polyzoa. 



By E. M. Brydone, F.G.S. 



(Continued from the April Number, p. 148.) 



(PLATE XXXII.) 



BESIDES the series of Membraniporellce last described there are 

 several other Cribrilinidae which develop a secondary aperture 

 in the same way, and the next four species are instances. 



Cribrilina transita, sp. nov. (PI. XXXII, Eig. 1.) 



Zoarium unilaminate, adherent. 



Zocecia of medium size, average length "7 to '75 mm. ; primarily 

 they are of the usual type with low slightly arched side walls and 

 arched front walls springing from the edges of the side walls, and 

 traversed by radiating furrows pierced in their outer half by short 

 and sometimes fairly broad slits, while at the inner ends there are 

 preserved very irregularly remains of a system of one or two 

 longitudinal rows of punctures ; six rows of paired furrows with or 

 without an unpaired one in the centre line seem to be the general 

 standard ; the aperture is roughly semicircular and its anterior lip 

 bears four tubercles ; in the secondary stage the side walls thicken 

 and rise, filling up the spaces between the front walls, but only 

 coalescing at occasional intervals ; the secondary aperture is formed 

 as usual from a denticle in the centre of the posterior lip of the 

 primary aperture which is produced over this aperture as a flat wide 

 bar, from the end of which (and from the sides of the primary 

 aperture) there arises very steeply a thick ring leaving two slits on 

 either side of the denticle and embracing the front part of the 

 ooeciura, on which the ring is flattened out somewhat angularly and 

 bears two small pores in the angles. 



Aviadaria small beak-shaped, narrow, and elongated, with strong 

 cross-bar close to the rounded end ; a pair are generally placed on 

 either side of the secondary aperture with their beaks directed 

 inwards and generally more or less downwards and merging into the 

 ring surrounding the aperture ; others are scattered irregularly over 

 the side walls. 



Ooscia large, globose, with small apertures cut well back, very 

 constant in occurrence. 



This species is the only one in the group to show Cribriline 

 perforation, and this fact and its tuberculated primary aperture 

 suggest relationship to Cribrilina furcifera, Bryd., 1 which itself 

 provides a half-way stage between this type of secondary aperture and 

 a simple aperture. It occurs quite rarely in the Uintacrinus band of 

 Hants and Sussex. 



1 Geol. Mag., 1910, p. 391, PI. XXX, Figs. 6-8. 



