202 DR. W. G. ElUKWOOD ON THE CKANIAL OSTEOLOGY OF 



NOTOPTEEIDJE. 

 NOTOPTEEFS KAPIBAT. 



The binder part of the cranium of Notopterus has been 

 described aud figured bj Bridge in his paper on the Air-bladder 

 aud Auditory Organ of Notopterus horneensis (Journ. Linn. Soc, 

 Zool. xxvii. 1900). 



Crannim (PI. 24. figs. 13, 14, and 15). — The appearance of the 

 cranium is remarkable on account of the five sharp ridges, two 

 paired and one median, which run lengthwise along it. The 

 median one is formed by the frontals and supraoccipital, the 

 upper lateral by the frontal, parietal, and epiotic, and the lower 

 lateral by the frontal and squamosal. Between the hind ends of 

 the two lateral ridges is a large foramen — the " lateral cranial 

 foramen " — leading, in the dried skull, directly into the cranial 

 cavity. It is bounded in front by the squamosal, behind by the 

 exoccipital, and above by the squamosal aud epiotic*. 



The supraoccipital crest is of considerable size, and in front 

 of it the two parietals meet in the middle line of the head. 

 The anterior half of each, is superficial, and is covered by skin 

 only, the posterior half is situated at a somewhat deeper level, 

 and is covered by muscle as well as skin. The squamosal 

 extends remarkably far forward, running completely over the 

 postfrontal, and resting its anterior end above the alisphenoid. 

 The epiotic is of small vertical extent. At the back of the 

 cranium, between the supraoccipital crest and the epiotic 

 prominence, is a depression occupied by trunk muscles, and into 

 the constitution of which the exoccipital enters largely. The 

 opisthotic is of moderate size ; it is set rather low down, and lies 

 beneath the squamosal and exoccipital, and touches the pro-otic 

 in front. 



The postfrontal is small aud does not enter into the hyo- 

 mandibular-cranial articulation. The articular surface for the 

 head of the hyomandibular is formed by the pro-otic and 

 squamosal in front, and by the exoccipital behind, a small 

 portion of the latter bone presenting itself between the 

 squamosal above and the opisthotic below and behind. The 

 exoccipitals just succeed in meeting above the foramen magnum, 

 but do not form any extensive suture. The base of the skull is 



* It is not surrounded by the squamosal (pterotic) as stated by Cope (Tr. 

 Amer. Phil. See, n. s. xiv. 1871, p. 454) ; neither is it bounded by the post- 

 frontal and squamosal as Boulenger states (Poissons du Bassin du Congo, 1901, 

 p. 115, and Ann. & Mag. Nat. Hist. [7] xiii. 1904, p. 164). 



