NO. 2177. FOSSIL FISHES IN NATt02^AL AIUSEUM— EASTMAN. 277 



ginal peaks, and extending close to the origin of the caudal fin; tlie latter nearly eqm- 

 lobate, its upper lobe with well-developed fulcra, and its width at distal extremity- 

 equalling about one-third the maximum depth of trunk. Dorsal fin with 50 or more 

 rays, caudal and anal each with a somewhat lesser number. (Paired fi ns not observed. ) 

 Scales ornamented externally with faint longitudinal striae and usually one longi- 

 tudinal ridge situated near the anterior border of each scale; attached surface coarsely 

 striated, the striae being nearly vertical on the deeper flank scales, but oblique on 

 those situated dorsally and ventrally and in the caudal region. Scales of the anterior 

 part of the trunk arranged in nearly vertical narrow bands, those toward the tail show- 

 ing a slight downward and backward obliquity, and those at the base of anal fin 

 reflexed forward toward the ventral margin. 



A single small specimen, catalogued as No. 4404, fairly well pre- 

 served and in counterpart, is contained in the United States National 

 Museum collection (from the R. D. Lacoe coll.). One of the halves of 

 this specimen is shown of the natural size in the accompanying plates, 

 and some of the details, such as scale ornament, lateral line, and 

 minute conical teeth are more clearly seen with the aid of a lens in 

 examinmg the opposite half, which is not figured. For so small a 

 specimen, the dorsal peak at the middle of the back is very promi- 

 nently elevated, and the appearances do not indicate that tliis is 

 merely an immature example of some larger form. An understand- 

 ing of the conformation of the head parts in this and related forms ^ 

 may be gamed from consulting the memoir by Dr. R. H. Traquair 

 "On the structure and affinities of the Platysomidae," published in 

 volume 29, 1879, of the Transactions of the Royal Society of Edin- 

 burgh. 



Formation and localitij. — Coal Measures; Mazon Creek, Grundy 

 County, Illinois. 



E. FISHES OF THE TRIASSIC SYSTEM. 



For the purpose of the present contribution it is not considered 

 practicable to enter into a lengthy or detailed account of the large 

 store of fossil fishes from Mesozoic and Cenozoic horizons belonging 

 to the collections of the United States National Museum, in view of the 

 fact that the majority of these belong to well-known genera, the 

 anatomical structure of which approaches rather closely to that of 

 modern forms, and the systematic position of which is pretty cer- 

 tainly ascertained. A few general remarks on the collection of post- 

 Palaeozoic fishes as a whole, followed by particular notice of certain 

 new or especially interesting species, will be sufficient for this section 

 of the report. 



Triassic fishes are extremely well represented in the Museum col- 

 lection. From the Triassic rocks of eastern North America very 

 extensive collections were made in the Connecticut Valley region dur- 



1 A restoration of the skeleton of Chdrodus granulosus (Young) is given in plate 5, figure 1, of this memoir 

 and one of Platysvmus striatus Agassiz in plate 6, figure 1. 



