Vol. 50.] THE INFERIOR OOLITE OF SHIPXON GORGE. 73 



has so far reduced the prodigality of d'Orbigny's nomenclature. 

 And yet I write this after giving my leisure hours of the past 

 three years to the study of the now genus Pergensia, so named in 

 recognition of Dr. Pergens's labour of revision. 



[Since the reading of this paper I have been aided by the gift of 

 specimens from Miss E. C. Jelly, the author of a most valuable 

 ' Synonymic Catalogue of Recent Marine Bryozoa.' Lehytliopora 

 and. Pcecilipora have many points of relationship with the new genus 

 Pergensia. To the general family likeness to the Cellcporidaj I had 

 previously drawn attention, in a comment upon the rostra and 

 apertures of one form. 



The globose ovieell-sacs of Pergensia find a parallel in the ovicells 

 of Leleythopora and Pcecilipora, genera which Mr. P. H. Mac- 

 Grillivray has so well worked out. We notice the same type of 

 mural and peristomial tubules, the same deep-seated opercula and 

 varied zocecial form. At the same time, it is not possible to escape 

 conviction as to there being two forms of ovicell : the supra-oral 

 type, which is a budding of minute cells at the back of the zocecium ; 

 and the ovicell-sac, which is either inter-zocecial or borne upon the 

 zocecial wall. The analogy of the cistern-cell of my Liassic genus 

 Cisternifera to the ovicell-sac is apparent, and in one instance there 

 appear to be the rudiments of a spouted process as in Cisternifera. 

 These lead to the ' cellules accessoires ' of d'Orbigny and possibly 

 to the ' giant cells ' of Busk and others. 



No author, so far as I know, has commented upon the functions 

 of the zooecial tubules of Lehytliopora, so plainly to be seen in the 

 specimen with which Miss Jelly has kindly supplied me. It has 

 seemed, in the study of my fossils, that they may develop around 

 and above the primary aperture. In the Liassic Cisternifera a 

 central tubule is a common feature ; in Pergensia I have noted it 

 in the species P. porifera. 



Some cells that I have called zocecia,with flat poriferous faces, may 

 be the columnar vicarious avicularia of Busk, Waters, and others ; 

 but there are points of structure, insufficiently worked out, which 

 make such association doubtful. 



The stipe of Lehytliopora and the mode of growth of the colony 

 around it explain the cylindrical axis of Pergensia, and show that its 

 'colonial' growth was after the same fashion. — November, 1893.] 



Pergensia, gen. nov. 



Zoarium piriform or cylindrical, with a central axial tube round 

 which the zooecia grow in spiral or irregularly spiral series. Zocecia 

 tubular, open or with terminal tubules ; ovicells supra-oral. Mural 

 openings, front or back. Ovicell-sacs : globose, nest-like cells enve- 

 loping the free ends of zocecia ; irregular swellings of the zoarial 

 wall, or globose cells borne on the zoarial wall. 



Pergensia nidulata, sp. nov. (PI. II. figs. 1,2: PI. III. figs. 1, 2, 

 3,4.) 

 Maximum zoarial length 4*0 mm., zoarial width 1*1 to 0-5 mm. ; 



