98 PROCEKDINGS OF THE GEOLOGICAL SOCIETY. [Juiie 14, 



tended to the additions made by M. Michelin * and Ilerr Roemcrf, the 

 characters of the Isle of Wight zoophyte will not be apparent ; but 

 should those structures be hereafter shown to exist, still as they do 

 not occur in the fossils on which the genus was founded, such species 

 would have to be removed from M. de Blainville's Fustulopora. It 

 is not considered necessary to prolong the comparison to other deli- 

 neated corals which present a limited amount, not an aggregate of 

 agreements ; and the compiler of these memoranda not being aware 

 of any established genus possessing a union of characters similar to 

 that already mentioned, and to be further noticed in the following 

 remarks, it is suggested that the Atherfield fossil may be designated 

 Chisma (x'^-A'"^ fssura), in allusion to the intervals between the 

 tubes. 



Chisma, n. g. 



Gen. char. — Tubular, branched ; tubes simple, in contact, or sepa- 

 rated by an interspace of variable breadth ; apertures irregularly 

 distributed over the w'hole surface, not mere tubular terminations ; 

 exterior of branches formed of more or less exposed portions of 

 tubes, progressively modified by external additions. 



Chisma furcillatum, n. sp, 



(Plate V. fig. 24 to 28.) 



Spec. char. — Branches cyhndrical, forked, occasionally anastomosed : 

 plane of successive bifurcations at right angles ; tubes variable in 

 form, slightly divergent, seldom bent suddenly outwards ; aperture 

 at distal extremity of exposed portion of the tubes ; in mature and 

 advanced states pustulose ; breadth of tube uniformly small in the 

 middle portion of the branch, considerable at the sides ; external 

 thickening of branches rugose. 



The specimen submitted to examination occupied an area about 

 one inch and a half square, throughout which the branches were 

 loosely distributed, but possibly at about their original relative di- 

 stance. There w'as not the slightest indication of a base or mode of 

 attachment. The diameter of the stems was nearly a line ; and no 

 marked diiference in dimension was noticed between the undivided 

 portion and the two shoots, near the point of separation. The bi- 

 furcations occurred at irregular distances, and the mode of branching 

 had not been strictly uniform ; but there was a marked tendency to 

 divide in alternate planes. Wherever the branches had come in 

 contact, a perfect union had taken place. 



A fragment (fig. 25) which was believed to represent in part an 

 unthickened, though not perfectly preserved exterior, displayed in the 

 upper portion, a surface composed of a variable amount of exposed 



* Iconog. Zoophyt. p. 210 to 212, pi. 53. figs. 2 to 6. 



t Versteineruugen des Norddeutsclicn Kreidegeb., ])p. 21, 22. pi. 5. fig. 23, 24. 



