1904.] OSTEOLOGY OF THE ELOPID^ AND ALBULID^, 65 



In Gonorhynchus the back of the basioccipital region of the 

 skull is hemispherical. This convexity of the occipital articulation 

 is not, however, peculiar to this genus, for Owen and Klein have 

 recorded the occurrence of such a convex articular surface in 

 Flstularia (Anat. of Yert. i. 1866, p. 107; and Jahresh. WUrtt. 

 1881, p. 325), and Klein in Syngnathus, Phyllopteryx, Gastero- 

 tokeus, and Ostracion (Jahresh. Wiirtt. 1885, p. 108). 



Temporal and Preoperctcla?' Series. — The post-temporal is a con- 

 stituent of the pectoral girdle rather than of the skull, but a 

 description of the skull can hardly be considered complete unless 

 mention be made of the manner in which the attachment with 

 the shoulder-girdle is effected, and this, very naturally, leads to a 

 consideration of the post-temporal bone itself. The post-temporal 

 bone is no dou.bt primarily a scale-bone of the sensory canal series. 

 It carries the lateral line forward to the supratemporal bone, and 

 the forward limb of the post-temporal is fairly well developed in 

 Engraulis and Chirocentrus. The other two limbs, to the epiotic 

 and opisthotic respectively, are usually much larger and better 

 defined than the forward limb that passes towards the supra- 

 temporal and squamosal. The extremity of the epiotic limb is 

 usually loosely attached above the epiotic prominence by a broad, 

 short ligament, but in CJiatoessus the connection is much more 

 intimate and the freedom of play is greatly restricted. In JVoto- 

 pter^is the epiotic limb is wanting. 



The opisthotic limb of the post -temporal is absent in Alepo- 

 cephalus, Coilia, and the Mormyridae ; in Gymnarchus both epiotic 

 and opisthotic limbs are wanting. In Engraulis the opisthotic 

 limb is attached to the back of the exoccipital in the absence of a 

 distinct opisthotic bone. The opisthotic limb lies deeper than the 

 epiotic limb, and appears not to be part of the dermal bone at all, 

 but rather one of the numerous intermuscular bones, at the back 

 of the cranium, which has acquired a secondary connection with 

 the post-temporal. The limb is always more or less rod-like 

 (except in Ilegalops), and unlike the two more superficial limbs. 

 In Clupeafinta and in Ghanos it forms the outermost element of 

 a series of thi'ee nearly parallel intermuscular bones, which 

 gradually increase in size from within outwards. The innermost 

 of the three is attached to that part of the exoccipital which forms 

 the lateral boundary of the foi-amen magnum ; the second is 

 attached to the exoccipital bone midway between this point and 

 that process of the opisthotic to which the deep limb of the post- 

 temporal is attached. The postei-ior ends of the inner and middle 

 rods spread out like stiff brushes among the trunk-muscles. In 

 Chirocentrus there are three brushes of tendon-bones on each side 

 of the back of the cranium ; one arises from the exoccipital 

 immediately dorso-laterally to the vertebral articulation, the 

 second from the exoccipital a little more laterally, and the third 

 from that j)art of the exoccipital that touches the mesial edge of 

 the opisthotic. This last tendon-bone lies immediately n^sial to 



Proc. Zool. Soc— 1904, Yol. II. No. Y. 5 



