FOSSIL AND RECENT 



107 



Fig. 52. Osmeroides lewesiensis (Mantell). Cranium in left lateral view. 

 Composite of several B.M.N.H. specimens. 



The preoperculum has two limbs, horizontal and vertical, the latter being the longer 

 and lying closely against the hyomandibular. The anterior margin of the pre- 

 operculum is thickened, particularly in the angle, and forms, together with the 

 hyomandibular, a prominent ridge for the origin of the adductor mandibulae. The 

 preoperculum is relatively narrow throughout its length. 



Pectoral girdle and fin. The supratemporal is triangular, ornamented with coarse 

 rugae and lies tightly against the posterior margin of the pterotic. The supra- 

 temporal is separated from its partner as in all albuloids. 



The post-temporal is relatively small, consisting essentially of two unequal limbs. 

 The upper limb projects forward to overlie the epiotic process, to which it was no 

 doubt connected by ligaments. The lower limb is very much smaller, both in length 

 and diameter, and projects antero-ventrally to lie against the intercalar. Posteriorly 

 the post-temporal overlies the top of the supracleithrum. The lateral line canal 

 ran through the post-temporal and continued within the dorsal part of the supra- 

 cleithrum. This latter element curves ventrally and overlies the dorsal part of the 

 cleithrum. Dorsally and ventrally the supracleithrum ends in rounded margins. 



The cleithrum is by far the largest element in the girdle, extending from the 

 posterior angle of the operculum to the medial surface of the interoperculum. The 

 anterior margin of the cleithrum is turned medially and thus presents a broad face 

 for the attachment of the sternohyoideus musculature. The posterior margin of 

 the cleithrum curves postero-ventrally to just above the fin insertion. At this 



