404 C. R. EASTMAN — JURASSIC FISHES FROM BLACK HILLS 



the lateral line distinctly; it is very well shown on both halves of the 

 specimen photographed in plate 47, figures 4 and 5. 



DETAILS OF FIGURED SPECIMENS 



The original of plate 45, figure 1, measures 13 centimeters from ex- 

 tremity of mandible to tip of ventral lobe of the tail, and its maximum 

 depth is 3 centimeters. Prominent scale features are the fine subdivision 

 of the ventral series, enlarged anal and striated postclavicular scales, 

 also the peg-and-socket articulation shown in several detached flank 

 scales. The facial plates are fairly distinct, and should be compared 

 with those shown in plate 46, figure 1 ; also with the wood cuts on pages 

 400 and 401. 



The fish shown in plate 45, figure 2, has a total length of about 11.5 

 centimeters, and maximum depth of 2.5 centimeters. Its impression in 

 counterpart shows various details more clearly than the actual fossil, 

 and for that reason was employed as a basis for the partly restored draw- 

 ing shown in plate 46, figure 2. The most perfect example of all, and 

 therefore selected as the type of this species, is represented in plate 46, 

 figure 1. It is preserved in the form of an impression, the opposite half 

 being lost, unfortunatel3^ The total length is about 13 centimeters, and 

 that of the head 2.5 centimeters, which is slightly less than the maxi- 

 mum depth of trunk. This specimen shows the head bones better than 

 all others, but still leaves much to be desired. The cranial roof has 

 been displaced upward, exposing the dorsal surface of the parieto-frontal 

 piece. The raised median line evidently represents the suture between 

 the paired frontals ; here it is straight, but in Eagnathus it forms a wavy 

 line, and the frontals are unsymmetrical. Indications of a circumorbital 

 ring are also to be seen on this specimen. The position of the anus is 

 marked by two enlarged scales befere the origin of tlie anal fin; the 

 pelvic is not preserved. 



Whether the original of plate 47, figure 1, should be included in the 

 same species with the rest is doubtful, as the roughened, almost papillose 

 condition of the scales seems attributable more to ornament than to cor- 

 rosion or wear. The anterior flank scales are deeper than in all other 

 specimens, some of them being nearly three times deeper than broad. 

 Branching longitudinal striae appear on the impressions of postclavicular 

 scales, and the cranial roof has the same roughened aspect as the scales. 

 A median suture is recognizable between the frontals, although not very 

 distinct. The clavicle is well displayed, as is also the base of the pec- 

 toral fin. Further material will be necessary to establish or disprove 



