DEVONIAN FISHES OF IOWA 187 



Fragments of this species are abundant in the Chemung rocks 

 at Leroy [Pennsylvania], and I select as typical of it a pair of 

 supraclavicular and adjacent pieces, which display its characters 

 best. The supraclavicle has lost the condylar articulation. 

 Both extremities display the unsculptured surface, and the 

 usual groove extends obliquely across the sculptured portion 

 at about two-fifths the length from one of the extremities. The 

 sculpture consists of obtuse tubercles with delicate radiate- 

 grooved bases, which are usually separated by spaces equal to 

 their own diameters, sometimes by narrower spaces, but never 

 by spaces which are wider. At some points they have a linear 

 arrangement. This sculpture is coarser than in the C. ameri- 

 canus [i. c, C. occidentalis] Newberry (see the Palaeozoic Fishes 

 of North America, by this author), but resembles that of C. 

 decipiens Agass., of Scotland. From this species the C. macro- 

 mus differs in the elongate form of the supraclavicle which is 

 relatively short and wide in the C. decipiens (see Agassiz, in the 

 Poissons du Vieux Gres Eouge, and Zittel, Handbuch der Pala- 

 ontologie). Length of supraclavicle, 35 mm; width just above 

 condyle, 16 mm. 



Formation and locality. Chemung group (Chautauquan) ; Le- 

 roy, Pennsylvania. 



Genus brachvdirus A. von Koenen. 

 (Syn. Pholidosteus Jaekel, 1907) 



A genus closely resembling Coccosteus and primitive species 

 of Dinichthys (e. g., D. halmodeus) in configuration of the head- 

 shield and system of abdominal armoring, but more laterally 

 compressed, functional margin of dental plates simply tren- 

 chant, and a fixed or movable spinous appendage (the so-called 

 "Ruderorgan" or "pectoral spine") developed in connection 

 with the antero-lateral plates in the pectoral region. Some minor 

 differences are also stated to exist with regard to the articular s 

 union between the headshield and plates of the dorsal armor, and 

 with regard to the uncovered area between the headshield and 

 dorsomedian plate. 



The earliest described species of this genus is B. bickensis, 

 from the Upper Devonian of Bicken, Nassau, which should still 

 be regarded as the genotype, although von Koenen at one time 

 expressed himself in favor of reuniting it with Coccosteus. The 

 cranial topography, however, as shown both by himself in 1883 



