﻿22 ACANTHODII. 



46305, 46305 a. Four specimens, two being destitute of the tail ; 

 also an imperfect left mandibular ramus with portions of 

 the dentition. Purchased, 1875. 



P. 132-6, P. 141-2, P. 144-8. Twelve specimens, the first preserved 

 in counterpart and shown, of the natural size, in PL I. 

 fig. 8. This specimen appears to exhibit the precise out- 

 line of the fish, without distortion, and all the fin-spines 

 are preserved in their natural positions. Two large teeth 

 remain in the upper jaw, but the bones and cartilages of 

 the head are obscure. A series of short, vertically elon- 

 gated impressions in the anterior portion of the trunk 

 have the appearance of neural arches ; though, if so, the 

 head has been somewhat displaced by crushing, for a few 

 of these impressions occur far forwards. The character- 

 istic form of the basal cartilage of one pectoral fin is indis- 

 tinctly shown. Portions of the membrane of the pelvic 

 and anal fins are exhibited, and the caudal is apparently 

 complete. Purchased, 1880. 



P. 1344. Two small specimens, and one measuring not less than 

 0-15 in length. Egerton Coll. 



The following specimen is not certainly determinable, but appears 

 to pertain to a large individual of this species : — 



P. 131. Caudal region and hinder portion of the abdominal region 

 of an Acanthodian fish, the specimen preserved in counter- 

 part and measuring 0-13 in length ; Lower Old Eed Sand- 

 stone, Turin Hill, near Forfar. Remains of the pectoral 

 spines show that these were of moderate size, slender, 

 arched, and finely ribbed. One dorsal spine (presumably 

 the second) is situated slightly behind the anal, and the 

 caudal fin is very robust. The scales are minute, smooth, 

 and faintly hollowed. Purchased, 1880. 



Family DIPLACANTHID./E. 



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

 spine. Pectoral arch with clavicular bones. 



Synopsis of Genera. 



A. Paired spines between pectoral and pelvic 

 fins insignificant or absent. 

 Teeth minute or absent; median pair of 



spines between pectorals Diphcanthus (p. 23). 



