﻿P ALTEON LSCTDJE. 441 



greatest depth of the trunk equalling about one quarter of the total 

 length of the fish. Head and opercular apparatus small, occupying 

 about one-fifth of the total length; external bones striated, the 

 striae upon the cranial roof being coarse, irregular, and more or 

 less subdivided. Paired fins small, the pelvic pair placed slightly 

 nearer to the anal than to the pectorals ; dorsal and anal fins equal 

 in size, triangular and short-based, the dorsal arising behind the 

 middle of the back, and the anal opposed to its hinder half. Scales 

 arge, those of the middle of the flank somewhat deeper than broad ; 

 a few series immediately behind the clavicle exhibiting fine posterior 

 flutings and denticulations. 



As pointed out by Giebel and Traquair, this species is truly re- 

 ferable to Amblypterus ; and the other so-called species of Palceo- 

 niscus, here regarded as synonyms, have also been assigned to 

 Amblypterus by Traquair. The type specimens were obtained from 

 the black shales of Kreuznach, and it appears to the present writer 

 that the various forms named by Troschel from the same formation 

 and locality owe their supposed distinctive features merely to dif- 

 ferences in crushing and state of preservation. The latter series 

 has already been identified with "Paloeoniscus " vratislaviensis by 

 Weiss, who gives an elaborate table of measurements to show the 

 great variation in the proportions of typical examples of P. vratis- 

 laviensis from Ruppersdorf, Bohemia. As a rule the last-mentioned 

 specimens do not attain so large a size as those from Kreuznach ; 

 but there are intermediate forms, and the examples from Miinster 

 Appel assigned by Agassiz to P. cluvernoyi are almost equally 

 small. 



The so-called Palceoniscus minutus, Agassiz (Poiss. Foss. vol. ii. 

 pt. i. pp. 4, 47, pi. viii. figs. 1-3), from Miinster Appel, of which 

 the type is in the Strassburg Museum, is probably the young of 

 this species. It is provisionally assigned to Awiblypterus by 

 Traquair, Quart. Journ. Geol. Soc. vol. xxxiii. p. 558. 



A very large imperfect fish from the Lower Permian of Semil, 

 Bohemia, described under the name of Palceoniscus luridus (J. J. 

 Heckel, Denkschr. k. Akad. Wiss., math.-naturw. CI. vol. xix. 1861, 

 p. 54, pi. iv.), is also difficultly distinguishable from Amblypterus 

 duvemoyi ; the specimen is in the Royal Bohemian Museum, 

 Prague. 



Form. <$f Log. Lower Permian : Rhenish Bavaria and Bohemia. 



37775-76. Two typical large specimens in black shale, of unknown 

 locality ; one larger than Agassiz's second type specimen, 

 and the other exhibiting well-preserved scales and median 

 fins. Purchased, 1863. 



