22 ILLINOIS BIOLOGICAL MONOGRAPHS [192 



The frontals (Figs. 2, 5, fr) are somewhat shorter than in Ophidon 

 and the surface between the orbits is markedly concave. The frontals 

 unite with the sphenotics in the usual position and form a part of the 

 orbit. The surface directly posterior to the orbit is somewhat depressed 

 and forms a ridge on the ventral surface in the posterior part of the 

 orbit. On the dorsal surface of the posterior portion of the bone there 

 is a granulated network arranged more or less in longitudinal ridges 

 with an irregular groove in the median line bounded by granulated 

 ridges. The ventral surface is comparatively smooth and the part 

 within the orbit is not porous as in Ophidon. There is a single ventral 

 flange-like process on each side of the median line forming a part of the 

 anterior boundary of the brain case. At the caudal end the flange is 

 thickened and unites with the alisphenoid. A ridge extends from this 

 point laterad to the edge of the bone at the place where it unites with 

 the sphenotic, forming a triangular pit between the ridge and the ante- 

 rior edge of the latter bone. There is also a small depression anterior 

 to the ridge between it and the flange. In some specimens the flange 

 comes in contact with the dorso-lateral process of the parasphenoid on 

 the anterior edge of the alisphenoid. 



The ventro-posterior edge of the sphenotic (Figs. 2, 5, spo), in con- 

 nection with the dorsal edge of the prootic dorsal to the arcade, forms 

 a facet for the articulation with the anterior head of the hyomandibular. 

 In Scorpionichthys the prootic forms nearly half of the facet while in 

 Ophidon it forms only a very minor part of it. The sphenotic forms the 

 greater part of the roof of the dilatator fossa, a condition slightly 

 different from Ophidon where the pterotic forms the roof. 



The pterotic (Figs. 2, 5, pto) forms only a small part of the dilita- 

 tor fossa and has a granulated surface. 



The alisphenoid (Fig. 5 als) is not porous and is not held between 

 the two ventral processes of the frontal. It lacks a foramen for the 

 passage of the cerebral vein such as Allis ( '09) found in Scorpaena and 

 others. It forms the dorsal edge of a large foramen which is otherwise 

 bounded by the edges of the prootic and the parasphenoid process. 



The basisphenoid and parasphenoid (Fig. 5, ps) are the same as in 

 Ophidon except that in the parasphenoid there is a small partition 

 between the two dorsal processes which separates the anterior and 

 posterior portions. 



The prootic (Figs. 2, 5, pro) possesses a flattened process on its 

 dorsal edge; this lies directly ventral to the hyomandibular facets and 

 causes the hyomandibular to extend laterally from the skuU. The ven- 

 tral surface of this process contains a rounded pit which extends dorsad, 

 almost between the hyomandibular facets. On the dorso-anterior edge, 

 immediately dorsal to the arcade, the bone forms a part of the facet 



