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main infraorbital canal, the canal lying immediately beneath the spinous ridge on the dorsal surface 

 of the bone and lodging but one sense organ of the line, innervated by the ranius oticus. The 

 preopercular canal joins the main infraorbital at the hind end of the section of canal enclosed in the 

 pterotic, the pterotic thus containing no post-preoj^ercular latero-sensory ossicle. 



B A S I C C I P I T A L. 



The basioccipital has, on its dorsal, cerebral surface, two large longitudinal grooves, one on 

 either side, these grooves occupying the entire dorsal surface of the anterior two-thirds of the bone, 

 excepting only the narrow median and lateral portions that form the bounding walls of the grooves. 

 Each groove is continued backward, as a recess, into the posterior third of the bone, the hind end 

 of each recess almost reaching the conical surface of the median vertebra-like depression on the hind 

 end of the bone. The posterior half or two thirds of the uncovered portion of each of these grooves 

 is roofed by a mesial, nearly horizontal process of the exoccipital of its side, the grooves thus becoming 

 large and deep recesses in the cranial floor. Each groove lodges the posterior portion of the sacculus 

 of its side, the anterior portion of the sacculus being lodged in the saccular groove on the cerebral 

 surface of the proötic. On the outer surface of the skull, the bounding wall of the basioccipital portion 

 of the saccular groove forms the posterior portion of the bulla acustica. 



On the dorsal surface of the basioccipital, between the hind ends of the saccular grooves, 

 there is a small median pit, sometimes separated into two parts by a tliin transversa partition, this 

 partition inclining from the mouth of the pit downward and backward toward its point. The pit, 

 whether simple or double, leads downward and backward almost to the point of the conical verte- 

 bra-like depression on the hind end of the bone, approaching that point so closely that it sometimes 

 is separated from it by a thin layer, only, of bone. This small median pit is evidently the homologue 

 of the cavum sinus imparis of Sagemehl's descriptions of the Characinidae and Cyprinidae, but it 

 is, in Scorpaena, wholly uncovered, the hind edges of the mesial processes of the exoccipitals reaching 

 only to its anterior edge and being restricted to roofing, on either side, a portion of the corresponding 

 saccular groove. This latter groove, it may be noted, is relatively small in the Characinidae and 

 Cyprinidae, its anterior end passing but slightly beyond the hind edge of the proötic; and the sacculi 

 of opposite sides are, in those fishes, connected by a canalis communicans, not found in Scorpaena. 



Posterior to the cavum sinus imparis, the narrow remaining portion of the dorsal surface 

 of the basioccipital slopes downward and backward to the hind end of the bone, is slightly concave 

 and forms a small bounding portion of the foramen magnum. On either side of the cavum sinus 

 imparis, there is a roughened surface which gives support to a corresponding portion of the ventral 

 edge of the exoccipital, and immediately anterior to this surface, on either side of the anterior end 

 of the cavum sinus imparis, the basioccipital encloses a small nodule of cartilage, a remnant of the 

 chondrocranium, which lies between it and the exoccipital. Anterior to this nodule of cartilage the 

 thin lateral edge of the basioccipital, on either side, is in sutural contact with the ventral edge of 

 the exoccipital; while the median ridge of the bone, which separates the saccular grooves, gives 

 support to the mesial edges of the mesial processes of the exoccipitals, a small remnant of cartilage 

 there intervening. 



On the ventral surface of the basioccipital there is a deep longitudinal groove, nearly circular 

 in transverse section. This groove lies between the bottoms of the saccular grooves, tapers gradually 

 to its hind end, and forms the posterior portion of the myodome. It opens on the ventral surface 



