450 BE W. G. RIDEWOUB ON TUE CRANIAL [DeC. 13, 



longitudinally by a bai' of cartilage, between the supraoccipital 

 and the fi'outal bones (wanting, howevei', in specimen B), and 

 another fontanelle between the antei-ioi' ends of the frontals. 

 The postei'ior temporal gi'oove is deep, but is not I'oofed over. 

 The gi'oove nari-ows away to a point anteiiorly, and situated near 

 its tei'mination is a temporal foiumen leading into the upper part 

 of the ci-anial cavity. Behind the temporal foiamen is a deep 

 pi-e-epiotic fossa, bounded above and in front by the paiietal, 

 below by the squamosal, and behind by the epiotic, and ter- 

 minating blindly against the deepei- part of the supraoccipital. 

 The lateiul temporal groove above the postfi-ontal is wide and 

 shallow. 



The opisthotic is veiy small, and abuts on the squamosal, 

 exoccipital, and pi-o-otic, but does not touch the epiotic. The 

 pro-otic is extensive, and neai-ly reaches the back of the cranium. 

 There is a small bulla, containing a vesicle of the swim-bladder, 

 situated a little above the centre of the latero-ventral face of the 

 pro-otic, and anothei- bulla, occurs in the squamosal and projects 

 slightly above the floor of the postei'ior tempoi'al groove. An 

 auditoiy fenestra, bounded by the pi'o-otic, exoccipital, and basi- 

 occipital, is present in the side of the cranium. 



At the front of the eye-muscle canal is situated a small basi- 

 sphenoid, bounded latei'ally by processes of the alisphenoids which 

 descend to meet the pro-otics. Thei-e is no descending pai't of the 

 basisphenoid to bisect the eye-muscle canal. The parasphenoid 

 projects a little behind the basioccipital, and has i-ight and left 

 posterior wings which bound the posterior outlet of the eye- 

 muscle canal. At its anterior end, where it meets the vomer, 

 the pai-asphenoid becomes considei'ably broader than in its 

 middle part. The \"omer pi'ojects in front of the mesethmoid, and 

 neithei' it noi- the pai'asphenoid beai's teeth. The ethmoid region 

 is comparatively short and well ossified, and there is no cartila- 

 ginous tract intervening between the mesethmoid and prefrontal. 

 The two prefrontals are closely united in the median plane of 

 the head. 



Temporal and Preoperc alar Series^ (text-fig. 119, p. 451). — The 

 post-temporal is comparatively large and has three limbs. The 

 uppei' one i-ests over the epiotic ; the opisthotic limb is long, rod- 

 like, and very slender ; and the third, which is pointed and shorter 

 than the othei* two, passes forwai'd to touch the back of the 

 supi'atemporal. The supi'atemporal is i-oughh^ trii'adiate, and its 

 antei'o-dorsal I'ay or limb is the largest ; it foi-ms a lateiul wall to 

 the unenclosed posterioi- tempoi-al gi'oove. The upper and lower 

 limbs of the pi-eopei'cular ai-e set at a very wide angle. The 

 interopercular has at its anterior end an ascending process which 

 flanks the inner surface of the lower part of the symplectic. 



* The reasons for including the preopercular and interopercular bones in this 

 series, and for excluding- tlieni from the opercular and branchiostegal series, are 

 given in a former paper (Proc. Zool. See. lOOl, ii. pp. 68 and 75). For reasons given 

 in the same paper, it is considered expedient to regard the post-temporal as a con- 

 stituent ot the skull. 



