On the chief Generic Types of Palceozoic Corals. 451 



piceous; antennas 15-jointed, joints twelfth and thirteenth white, 

 tive or six of the basal joints rufo-piceouSj as are also the 

 palpi ; the prothorax oblong-quadrate, narrowly margined, and 

 with a longitudinal impressed line not extending to the pos- 

 terior margin ; not winged ; the abdomen smooth and shining; 

 the basal half of the segments with fine shallow punctures ; 

 the apical segment with a deeply impressed longitudinal line, 

 its posterior margin emarginate ; the forceps very stout, trian- 

 gular at the base, curved inwardly beyond the middle, acute 

 at the apex, their inner margin crenulated. 

 (Coll. by Gulliver.) 



This species has a close general resemblance to F. maritima. 



LIII. — Contrihutions to the Study of the chief Generic 

 Types of the Palceozoic Corals. By James Thomson, 

 F.Cx.S., and H. Alleyne Nicholson, M.D., D.Sc, 

 F.R.S.E., Professor of Natural History in the University 

 of St. Andrews. 



[Continued frojn p. 305.] 

 [Plates XXI.-XXV.] 



Genus Clisiophyllum. 



Clmo}}hyllum, Dana (in parte), Explor. Exped. vol. \'iii. Zoophytes, 

 p. 3G1, pi. xxvi. fig. 6 (cjet. exclus.), 1846. 



Gen. char. Corallum simple, cono-cylindrical, or turbinate. 

 Epitheca complete, sometimes thin, sometimes thick, marked 

 with constrictions and accretion-ridges. Calice of variable 

 depth, its floor exhibiting a conical boss in the centre. The 

 surface of the boss is marked with a system of spirally bent 

 or sometimes straight lamellse, which are attached to the inner 

 margins of the primary septa by the intervention of a system 

 of delicate dissepiments, and, on the other hand, pass upwards 

 to a median columcllar crest on the crown of the boss. Septa 

 well developed, of two orders, the primary septa never ex- 

 tending further inwards than near to the outer margins of 

 the central boss. Internal structure triareal. Central area 

 ("interlamellar space ") formed partly by a system of vertical, 

 spirally twisted or straight lamcUaj, and partly by a system 

 of vesicular tabulse, which intersect the former obliquely, and 

 arc directed upwards and inwards to join in the columel- 

 larian line. Intermediate area (" intcrlocular space ") formed 

 by an outward extension of the tabuhr; in large nearly hori- 

 zontal vesicles. External area (" interseptal space ") formed 



30* 



