290 Mr. J. Thomson and Dr. H. A. Nicholson on the 



developed, nearly as large as, and similar to, that in G. tuber- 

 culatus. 



Upper inner incisors long and slender, with a second, very 

 small, external cusp ; upper outer incisor, on each side, very 

 small, scarcely as long as the cingulum of the inner incisor. 

 Second upper premolar close to the canine ; the first small 

 premolar in the angle between the canine and the second pre- 

 molar, and visible only with aid of a lens. Lower incisors 

 very small, trifid, not crowded. First lower premolar scarcely 

 equal to half the second premolar in vertical extent. 



Length (of an adult male preserved in alcohol), head and 

 body 1'95 inch, tail 1'75, head 0*55, ear 0*4, tragus 0"18, 

 forearm 1'4, thumb 0*25, second finger 2*5, fourth finger 1*9, 

 tibia 0'6, foot and claws 0'3. 



Hob. Queensland. Type in the collection of the British 

 Museum. 



XXVIII. — Contributi07i3 to the Study of the chief Generic 

 Types of the Falceozoic Corals. By James Thomson, 

 F.(T.S.,'and H. Alleyne Nicholson, M.D., D.Sc, 

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

 of St. Andrews. 



[Continued from p. 128.] 



[Plates XII., XIV., XV., XVI., & XVII.] 



Genus LiTHOSTROTION. 



Lithostrotion, Lh^v^-d, Litbophyl. Britann. Ichnographia, epist. 6, 

 tab. xxiii. 1699. 



Gen. char. Corallum compound, fasciculate or astrseiform. 

 Corallites surrounded by a complete epitheca ; an imperfect 

 or ill-defined accessory wall is usually present. Septa well 

 developed, the primary septa extending from the outer wall 

 nearly to (or sometimes quite to) the columella. A compact, 

 styliform, laterally compressed columella is present. Central 

 area of each corallite formed by irregular, generally somewhat 

 elevated tabulge. Between the central tabulate area and the 

 wall the interseptal loculi are filled with dissepiments, pro- 

 ducing in longitudinal sections a series of small lenticular 

 cells arranged in layers which are directed upwards and 

 outwards. 



The corallum in Lithostrotion is never simple. Sometimes 

 it is fasciculate, and is composed of more or less cylindrical 

 flexuous corallites; at other times the corallum is astrjeiform, 



