﻿Vol. 6 1.] SEQUENCE IN THE BRISTOL AEEA. 285 



The following figures of horizontal sections, given in Thomson's 

 paper, Proc. Phil. Soc. Glasgow, vol. xiv (1883), seem to denote 

 species closely related to our form : — 



Dibunophyttum M'Chesneyi, Nich. & Thorns., pi. xii, figs. 2-2 b. 

 Aspidophyllum obovatum, Thorns., pl.xiii, fig. 7. 

 Aspidophyllum Konincki, Thorns., pi. xiii, fig. 8. 



' Clisiophyllum.' 



< Clisiophyllum ' (Cabcinophyllum) 6. (PI. XXIV, figs. 3-3 6.) 



This species cannot be regarded as, in any sense, a typical member 

 of the genus Clisiophyllum ; it is only placed here tentatively, until 

 its real affinities are better understood. 



Form : conical, usually elongated, and often curved. 



Epitheca : strongly rugose and, in specimens from D 1? usually 

 with hollow ' roots.' 



Horizontal Section. — Central area marked out by a strongly- 

 defined oval boundary. 



Mesial plate short, and entirely surrounded by a network of 

 anastomosing intersections. Lamella? almost as numerous as the 

 primary septa. The mesial plate and lamella? are, however, often 

 indistinct. 



Primary septa, usually 33 in number, well spaced, thick, and not 

 extending as far as the outer wall. Secondary septa short and stout, 

 projecting inwards from the thick inner wall. 



Fossula : there is scarcely a suggestion of septal break. 



Peripheral area : narrow, but composed of large vesicles, and not 

 radiated by prolongations of the septa. The loose texture of 

 the peripheral area renders it peculiarly liable to destruction, a fact 

 which affords an easy method of recognizing weathered specimens. 

 In its structural details, this species presents a general resemblance 

 both to Lonsdalia and to Campophyllum aff. Murchisoni ; the re- 

 semblance to the former is, however, doubtless deceptive, whereas 

 the resemblance to the latter is probably owing to true affinity 

 (see below, p. 287). 



The only previously-described form to which ' Clisiophyllum ' 6 

 appears to be closely related is Carcinophyllum Kirsopianum, 

 Thorns., Proc. Phil. Soc. Glasgow, vol. xiv (1883) pi. xii, fig. 9 a. 

 This species agrees in all essential characters with our form, but 

 has no mesial plate. Since, however, the mesial plate is not 

 distinguishable, in certain sections which I have had cut from 

 undoubted specimens of our coral, the reference of our species to 

 Carcinophyllum seems justified. 



Section III. (The Cymatiophyllum- Group). 



Clisiophyllids which resemble the Dibunophyllum-grou]) in all 

 characters, except the special thickening of the mesial plate. The 

 boss has consequently no crest, but is gently rounded, flattened 

 or slightly depressed on the top. 



