DEVONIC FISHES OF THE NEW YORK FORMATIONS 1 57 



lines. The only American species known is P. delicatula Newberry, 

 from the Chemung of Bradford county, Pennsylvania. Accompanying the 

 latter, but of still more problematical nature, are plates with arrowheadlike 

 ornamentation, described by Newberry under the name of S p h e n o- 

 p h o r u s 1 i 1 1 e y i.' Certain elliptical plates having a closely similar style 

 of ornamentation are also known from the Hamilton of Milwaukee. From 

 this locality also are obtained a number of peculiar plates, possibly repre- 

 senting the dorsomedian of unknown forms, two such being shown in plate 

 2, figures 3 and 4. Aspidichthys, Phyllolepis, and possibly also Holonema, 

 are represented in the European Devonic, and one species from the Devonic 

 of Manitoba is doubtfully referred to Aspidichthys (A. ? n o t a b i 1 i s) by 



Whiteaves. 



Order CXENODIPTERINI 



Body fusiform, without dermal armor. Skeleton and chondrocranium 

 partially ossified, skull autostylic, premaxillae and rnaxillae absent. Cranial 

 roof bones small, and, like the squamation, with or without ganoin invest- 

 ment. Nostrils inferiorly situated; jugular plates present or not. Tail 

 heterocercal or apparently diphycercal (gephyrocercal). Anal fin always 

 distinct, the remaining median fins either discontinuous or becoming 

 coalesced. Paired fins acutely lobate. Secondary pectoral arch consisting 

 of ossified supraclavicular and clavicle ; pelvic arch present. Dentition 

 consisting of large tritoral dental plates supported by the palato-pterygoid 

 and splenial bones ; a marginal series of teeth above and below also some- 

 times present, but never any vomerine teeth. 



The structure of this singularly interesting order of Paleozoic fishes 

 has been investigated in minute detail by Pander, Traquair and others, 

 and particularly within the last dozen years or so its .relations to modern 

 lung fishes have engaged profound attention amongst students of ichthy- 

 ology and paleontology. Recent discussion has centered around two rival 

 theories, as we have already seen. According to the first, which has 

 steadily gained in ascendancy, the typical Dipnoans of the Devonic are 



' The generic name being preoccupied, Oestophorus has been proposed as a substitute 

 by S. A. Miller. Plates of this description occur also in the Hamilton. 



