EASTMAN: FOSSIL LEPIDOSTEIDS. 73 



Regarding the fine head of Lepidosteus atrox (Plate 2) procured by Mr. 

 Charles Schuchert for the United States National Museum while collecting in 

 Wyoming last summer, Mr. Lucas writes : — 



" The specimen (Cat. No. 4755) consists of a little more than the anterior 

 half of an individual of about the same size as that belonging to the Museum 

 of Comparative Zoology at Cambridge. It lies upon the ventral surface, and 

 while the body has of course been flattened, the cranium has suflFered but little 

 from compression, and is almost as favorable for study as a fresh gar would be. 



" The general form of the cranium is intermediate between that of Lepidos- 

 teics osseus and L. tristoechus, the muzzle being slightly wider than in the first- 

 named and narrower than in the latter, so that there is no such obvious notch 

 towards the anterior part of the ethmonasals as appears in L. tristcechus. At 

 the same time the back of the cranium is proportionately wider in the Eocene 

 than in the living species, the result being that the skull of L. atrox tapers 

 somewhat abruptly from behind forward. 



" The right vomer is turned outwards exposing its anterior end, and a frac- 

 ture across the muzzle brings to view a section of the palatines ; from these 

 exposures it is possible to state that both vomers and palatines are dentigerous, 

 while in the lower jaw teeth are visible on the dentary. There is no apparent 

 difference between the dentition of L. tristcechus and L. atrox save that in the 

 present specimen none of the teeth are so large as in the living species. The 

 Cambridge example, however, shows this to be an individual peculiarity. Two 

 nasal plates are present on either side as in existing gars, and the maxillary 

 segments are seven in number, or one more than in the two examples of the 

 Alligator gar available for comparison. The ethmonasals, especially the ex- 

 ternal sculptured parts, are, as previously noted, narrower in L. atrox than in 

 L. tristoechus. The frontals are much the same in the two species, but the 

 parietals and squamosals are a little shorter and wider in the fossil than in the 

 lixnug gar. The circuuiorbitals are displaced and few of them visible, but such 

 as can be seen are notably thick. The same remark applies to the operculum 

 and suboperculum, for although of practically the same size as in L. tristoechus, 

 they are decidedly thicker. The cranial bones are also heavy, and their sculp- 

 turing while well defined is a trifle finer and decidedly more granular." 



Principal Measurements of the Washington Cranium {cf. Plate 2). 



Length from extreme tip of nasals to end of supratemporals .... 34.2 cm. 



Length of maxillary I.5 g 



Length of exposed portion of ethmonasal along suture 12.7 



Length of frontals along median suture 13.7 



Length of parietals along median suture 4.6 



Width across anterior part of ethmonasal 4.6 



Width across exposed portion of ethmonasal 2.2 



Maximum width across anterior portion of both frontals 5. 



Maximum width across posterior portion of both frontals, at junction 



with sqnamosals 93 



Maximum width between outer borders of right and left squamosals . 14. 



