﻿20 ACANTHODII. 



Cheiracanthus grandispinus, M'Coy. 



848. Chiraeanthus (jrandispiims, F. M'Coy, Ann. Mag. Nat. Hist. [2] 



vol. ii. p. 300. 

 1855. Chiraeanthus </ra?idispinus, F. M'Coy, Brit. Palseoz. Foss. p. 582, 



pi. iis. fig. 1. 

 1888. Cheiracanthus grandispinus, R. H. Traquair, Geol. Mag. [3] 



vol. v. p. 512. 



Type. Imperfect fish ; Woodwardian Museum, Cambridge. 



An imperfectly known species, attaining a length of about 0*25- 

 0-3. Body comparatively deep and robust. Fin-spines extremely 

 stout and longitudinally ribbed, the length of the pectorals not 

 equalling the depth of the trunk at their point of insertion. Pelvic 

 fins arising midway between the pectorals and the anal, and the 

 dorsal midway between the pelvics and the anal. Scales relatively 

 small. 



Form. S[ Log. Lower Old Red Sandstone : Orkney Isles, Scotland. 



39186. Middle portion of trunk, with pelvic, dorsal, and anal spines. 



Bowerbcmk Coll. 



41130. Imperfect head and trunk, wanting the extremity of the 

 caudal region. Bryson Coll. 



P. 178-9. Two imperfectly preserved specimens, the first showing 

 remains of the head and anterior portion of the abdominal 

 region, the second only wanting the extremity of the tail. 



Purchased, 1881. 



Family ISCHNACANTHIDiE. 



Two dorsal fins present, both these and the anal with an anterior 

 spine. Clavicular bones absent. 



This family is represented only by the type genus. 



Genus IS CHN ACANTHUS, Powrie. 



[Quart. Journ. Geol. Soc. vol. xx. 1864, p. 419.] 



Syn. Ictinocephalus, D. Page, Rep. Brit. Assoc. 1858, Trans. Sect. 

 p. 104 (undefined). 



Body fusiform, laterally compressed. Dentition prominent, con- 

 sisting of few large conical teeth, the interspaces between these 

 teeth being occupied by a close series of minute cusps, all apparently 

 in firm connection with a membrane-bone in both jaws. ISTo median 

 pair of spines attached to the pectoral arch between the pectoral 

 fin-spines. 



