﻿ACANTHOPIT. 



spines broad and robust, much laterally compressed, very slightly 

 arched, with ono very prominent, oblique, lougitudinal ridge and 

 groove and several minor grooves ; pelvic fin-spines relatively small, 

 scarcely attaining one quarter the size of the pectorals. Pelvic fins 

 placed far forwards, the length of the space between this pair and 

 the pectorals equalling about one half that of the space between it 

 and the anal. Anal fin-spine half as large as the pectoral ; dorsal 

 still slightly smaller, situated a short distance behind the anal. 

 Scales smooth or with a median pit. 



According to the latest memoir on the subject — that by Kner — 

 A. bronni is distinguished from the so-called A. gracilis by its less 

 slender proportions, its relatively smaller scales, and the more poste- 

 rior situation of the pelvic fins. The two forms, however, are deter- 

 mined as occurring together both in East and West Germany ; and 

 all the examples figured by Kner from Saarbriick (Rhenish Prussia) 

 are named A. gracilis. 



An examination of the series of specimens mentioned below, sug- 

 gests to the present writer that the comparatively robust appearance 

 of the type specimens of A. bronni and other fossils in the Saar- 

 briick nodules assigned to this species is due entirely to imperfect 

 preservation. The fishes have been buried in a coiled-up state, 

 while the skin with its scales has been displaced by crushing ; and, 

 when a sharp outline is distinguishable, the body appears quite as 

 slender as that of the well-preserved typical examples of A. gracilis 

 occurring in the fine shale of Klein Neundorf. The size of the 

 scales is also inconstant, and we can therefore, as yet, determine 

 only one species in the German Rothliegendes. 



Kner describes, as characteristic of this species, the presence of a 

 small spine bounding the posterior margin of the pectoral fin. The 

 statement, however, seems to have been based upon a mistake in 

 observation ; for the specimens in the Collection exhibit no such 

 spine, and in one case cited (Kner, pi. v. fig. 1) it may well be a 

 fragment of an ordinary pectoral, while in the other case (Kner, 

 pi. vi. fig. 1) it is probably the pelvic fin-spine somewhat displaced. 



Form. 6f Loc. Lower Permian (Ptotbliegendes) : Germany. 



22658 a. A small specimen completely coiled upon itself, in a 

 nodule ; Saarbriick, Rhenish Prussia. The circum- 

 orbital plates and the gill-arches are shown in the region 

 of the head. Purchased, 1848. 



40048-50. One nodule with obscure remains of a fish of moderate 

 size ; another with remains of a large head and anterior 

 portion of the abdominal region ; and a third nodule con- 



