110 CATALOG OF FOSSIL FISHES IN THE MUSEUM 



Ptyctodus compresses Eastman 



(PL 36, figs. 3-9, II, 12; PI. 37, figs. 1-8, 10-13) 



This species is represented in the collection by over three dozen 

 specimens, collected at various time's by Mr: Bryant, from the Cono- 

 dont bed, at Eighteen Mile Creek. It is the finest series of ptycto- 

 dont plates of one species ever assembled, some of the specimens being 

 exquisitely preserved and showing all the details of structure. 



E 1911 A rather large, perfect right lower dental plate, (PI. 37, fig. 

 1 2) partly embedded in limestone ; in inner view. Length 

 46 mm.; height at beak, 14; max. width of tritor, 6. 

 The rows of punctae are well shown, as is also the com- 

 pressed edge back of the tritor. 



£ 1912 A large, much worn, left lower dental plate (PI. 36, fig. 9). 

 This is the largest specimen of this species ever found. 

 It is 68 mm. in length (including in this 5 mm. allowed 

 for missing posterior extremity). Max. width of tritor, 

 8 mm. The tritor is much worn, posteriorly excavated 

 so that the region back of the tritor appears to rise up- 

 ward. The linear arrangment of the punctae is entirely 

 obliterated. 



E 1914 Five right lower dental plates. One, in inner view (PI. 37, 

 fig. 6), is 43 mm. in length (including in this 3 mm. 

 allowed for missing posterior extremity). It is one of the 

 most perfect dental plates ever f omid. It shows well the 

 spiniferous process below the symphyseal region. The 

 beak is pointed, and the cutting edge following it, as well 

 as the tritor, are well preserved. It shows the inferior 

 margin of the inner side, which is very rarely preserved. 

 The others are shown in Plate 36, figures 3, 8, 12; Plate 

 37, %• 4- 



E 1914-A Two left lower dental plates (PI. 37, figs. 3 and 5), one of 

 them embedded with its lower margin in matrix. 



E 1916 Two rather small right upper dental plates. We figure one 

 of these in Plate 36, figure 5. 



E 1917 Three left upper dental plates, one of them in matrix (PI. 

 36, fig. 6; PI. 37, fig. 2). 



