Natural History of East Finmarlc. 595 



Specimens here described are from Spitsbergen (Siiiift), and 

 others were found growing luxuriantly on a shell of N'eptunea 

 fornicata, given me by Prof. Loven, from the Stockholm 

 Museum, and which was dredged by the ' Vega/ lat. 66" 

 58' N., long. 171° 35' E., that is"^, in Bering Strait; while the 

 type described by Hincks came from Queen Charlotte Islands, 

 and the early stage of development figured by Waters from 

 Franz-Josef Land. It is thus a circumpolar form. 



Genus Oochilixa, gen. nov. 



Type^ Oochilina [Membranipora] crassimarginata, Hincks. 



Zooecia with front wall entirely membranous, ovate (long 

 ovate or short ovate, more rarely linguiform), depressed, 

 with crenated or smooth margin, no lateral spines. A round, 

 oval, or oblong avicularian chamber developed between and 

 taking the place of a zooccium ; avicularium typically with a 

 complete bar, the mandible rounded (or acnte). OcEcium 

 semiglobose. (Pore-chambers ?) 



Besides O. crassimarginata and 0. tensa, the following are 

 apparently referable to this genus : M. temiirostris, velata, 

 plana, and valde-munita, of Hincks ; M. papulifera and 

 Biflustra perfragilis, MacGillivray ; and perhaps M. greyaria, 

 Heller. 



The bar of the avicularium is complete and the mandible 

 rounded in O. crassimarginata and O. tensa ; but the bar is 

 incomplete and the mandible acute in some of the species 

 which I have temporarily assigned to the genus. 



Oochilina tensa, sp. n. (PL XIII. fig. 12.) 



Spreading on stones as a thin coating in large patches. 

 Zooecia normally oval, but owing to pressure on each other, 

 &c., they assume various forms — nearly oblong, linguiform, 

 or lozenge-shaped ; the frontal membrane is very thin, 

 delicate, and transparent ; the side walls are lightly formed, 

 only showing symptoms here and there of crenulation of the 

 border. In a separate chamber between the zorecia is situated 

 an avicularium, small and not nearly occupying the whole 

 of the top of the chamber; the bar complete, the mandible 

 rounded ; the avicularium is perpendicularly placed. Ooecia 

 subglobose, well raised, porcellanous, and of a milk-white 

 colour and smooth surface. 



On pieces of stone, chiefly granite; dredged in the Bergen 

 Fiord in 1878, and in the Hardanger Fiord in 1879. 



It would be very easy to mistake this delicate ci'ceping 

 form for incrusting Flvstra Barleei, but in that species the 

 avicularium holds a decidedly oblique position, and the 



41* 



