DEVONIAN FISHES OF IOWA 117 



nounced description than is found in the young forms of any 

 hitherto described species, and this together with the great deli- 

 cacy of its ornamentation distinguishes it as new. ' ' * The author 

 further remarks in the same connection that ' ' Gyracanthus has 

 hitherto not been known to exist below the horizon of the Car- 

 boniferous rocks. Its occurrence in the Lower Devonian of Can- 

 ada is therefore as interesting a fact as the occurrence of Cephal- 

 aspis in the Upper Devonian of the same country." Newberry, 

 however, in his Monograph of 1889, had founded the species G. 

 slienvoodi upon the evidence of ten spines contained in an erratic 

 block seven by nine inches in dimensions, within which were 

 also embedded teeth and scales of Holoptychius, the whole easily 

 recognizable as having been derived from the Catskill sandstone 

 in Pennsylvania. More recently the same species has been found 

 in the Chemung of Cattaraugus county and elsewhere in the 

 state of New York. Hence there are at present three clearly dis- 

 tinct species of Gyracanthus ranging from the supposed Lower 

 to the uppermost Devonian in eastern North America. The asso- 

 ciation in the same matrix of as many as ten spines belonging 

 to at least half as many individuals, assuming that they were 

 all pectoral fin-defenses, and the inclusion therewith of remains 

 of a large Crossopterygian fish is indeed a remarkable circum- 

 stance. A convenient explanation of the facts would be to 

 suggest that the spines are preserved as part of the stomach 

 contents of the larger fish whose remains are indicated by scales 

 and teeth, and whose food-habits might well have included such 

 prey as Acanthodian sharks. 



Formation and locality. Base of Marcellus division of the 

 Erian (Middle Devonian) ; Stafford, New York. Holotype pre- 

 served in the New York State Museum at Albany. 



Subclass HOLOCEPHALI. 



Skeleton entirely cartilaginous, in which no true bone is devel- 

 oped; mandibular suspensorium and pterygoquadrate cartilage 

 fused with the cranium (autostylic) ; exoskeleton, when present, 

 structurally identical with the teeth. Tail heterocercal, gill-slits 



*Traquair, R. H., Notes on the Devonian Fishes of Scaumenac Bay and Camp- 

 belltown in Canada. Geol. Mag. 1890, dec. 3, vol. 7, p. 21. — Whiteaves, J. F., 

 Supplementary Notes. Trans. Roy. Soc. Canada, 1908, ser. 3, 1, sect. 4, p. 2-58. 



