DEVONIC FISHES OF THE NEW YORK FORMATIONS 33 



history of Asterolepids back over a longer time interval than has previously 

 been known for this group. The so called "Astraspis desiderata" 

 of Walcott, from the Lower Siluric of Canyon City, Col., by some 

 conjecturally referred to the Asterolepidae, is of extremely doubtful 

 position. 



Family asxerolef-idae 



Head and body covered with dermal plates which are externally sculp- 

 tured and tuberculate, the dorsal and ventral shields of the trunk firmly 

 united by the lateral plates. Orbits very closely approximate, separated by 

 a loose interorbital median plate. Position of the nasal organs not definitely 

 known. One pair of paddlelike appendages, completely incased in osseous 

 plates, and articulated by a complex joint with the anterior ventrolateral 

 plates of the trunk. Sensory canal system well developed. Tail either 

 naked or scaly ; one or two dorsal fins, and a completely heterocercal 

 caudal. 



To form an adequate conception of the creatures indicated by numerous 

 fragments of Asterolepid armor from the Upper Devonic of New York and 

 Pennsylvania, it is necessary to pay particular attention to recent work that 

 has been done in the investigation of Scottish and Canadian species. As 

 has already been observed, the principal advance that has been made within 

 late years is owing to the researches of Dr R. H. Traquair of Edinburgh, 

 Professor William Patten of Dartmouth, and Dr Otto Jaekel of Berlin, their 

 results being scattered through a very considerable number of papers. 

 Without doubt the most notable contribution, and at the same time one of 

 the most authoritative, is Dr Traquair's Monograph on the Astcj'olepidae, 

 still in course of publication by the Palaeontographical Society of Great 

 Britain. As students who have not access to special libraries can hardly be 

 supposed to be familiar with the parts of this work already published, we 

 shall probably do well to present here a condensed account of the Astero- 

 lepid organization, taken almost verbatim from the Scottish author's descrip- 

 tions. , Acknowledgments are due to the same source for the accompanying 

 text figures of Pterichthys and Bothriolepis ; and we are also indebted to 



