6o4 



The Crossopterygii 



Lcpisostens. In Glypiopomns these scales are sculptured, in 

 the others smooth. In Osteolepis, Thursius, Diplopterus, and 

 Glvptopoinns a pineal foramen is present on the top of the head. 

 This is wanting in Parabatrachiis (Megalichthys of authors). 

 In Osteolepis, Thursius, and Parabatrachiis the tail is heterocercal, 



'..'■s^^^-<iiif^!!^Wvi' 



Fig. 374. — Oyroptychius microlepidotug Agassiz. Devonian. Family Megalich- 



thyidm. (After Pander. ) 



while in Diplopterus and Glyptopoinus it is diphycercal. Osteo- 

 lepis iiiacrolepidotiis and numerous other species occur in the 

 Lower Devonian. Diplopterus agassizii is common in the same 

 Imrizon. Megalichthys hibbcrti is found in the coal-measures, 

 and Glyptopoinus niinimus in the Upper Devonian. Palceostens 

 IS another genus recently described. 



The OiiyeJiodoiitidcc are known from a few fragments of 

 Onychodns sigitioides from the Lower Devonian of Ohio and 

 Oityehodiis anglieits from England. 



Order Actinistia. — In the Actinistia there is a single fin-ray 

 to each basal bone, the axonosts of each ray fused in a single 



-■^^ 



Fig. 375. — Gwlacanihus elegans Newberry. From the Ohio Carboniferous, showing 

 air-bladder. (After Dean.) ' " 



piece. The notochord is persistent, causing the back-bone 

 in frissils to appear hollow, the cartilaginous material leaving 

 no trace in the rocks. The genera and species are numerous, 

 ranging from the Subcarboniferous to the Upper Cretaceous, 

 many of them belonging to Cadaeanthus, the chief genus of the 



