202 PEDICULATI. 



prolongation of the opercles and of the humeral arch. The skull 

 proper is rather elevated and of moderate length ; the crown of the 

 head convex, with a longitudinal median groove, which is widened 

 anteriorly and posteriorly ; there is no trace of an occipital crest- 

 Having for examination a skeleton with the rostral process well 

 developed, I find the following structure of this part of the skull, 

 differing therein from the account given by Valenciennes : — The 

 principal frontal bones advance to before the orbit, their extremities 

 being united to the praefrohtaLs, which have a subvertical position, 

 forming the anterior portion of the orbit. The two principal frontal 

 bones and the two praefrontals coalesce at their extiemities into one 

 point, which in the short-snouted specimens forms a portion of the 

 front part of the snout ; they leave between them a tunnel-like 

 space, in which the rostral tentacle and the processes of the inter- 

 maxillaries move. Bony tubercles surround the point in which the 

 frontal bones meet, forming a swelling, in which is inserted the base 

 of the rostral process : we consider this process, which is a bone by 

 itself, as the united turhinal bones. The praeorbital and the other 

 suborbital bones are absent. The maxillary bone is not dilated ; it is 

 received in a shallow groove formed by a ridge on the posterior part 

 of the mandible. The intermaxillary is not much shorter than the 

 maxillary, and dilated posteriorly into a curved process ; its arti- 

 culary processes are long. The head of the vomer is broad, flat, 

 armed with a broad subquadrangular patch of villiform teeth ; a 

 smaller patch belonging to the palatine bone is contiguous with the 

 former. The hyoid bones are covered with a large patch of viUi- 

 form teeth, extending backwards to the lower pharyngeals. 

 The base of the cranium is rather compressed. 

 The preeoperculum does not extend forwards to the mandible. 

 The interoperculum is long, styUform, ascending obliquely backwards, 

 and swollen behind the praeoperculum into a broad knob, which cor- 

 responds to a notch of the suboperculum. The operculum is elongate, 

 branching oif posteriorly into two lobes. The suboperculum is the 

 largest of all the opercular pieces and composed of three parts : the 

 anterior meets the interoperculum, is narrow and swollen at its front 

 eJttremity ; the posterior is lanceolate, forming the hindmost portion 

 of the skull ; and, finally, the middle is rhomboidal, situated behind 

 the operculum, between the lobes of which it is received. 



The structure of the humeral arch is very simple ; I can distin- 

 gixish only three bones: a furcula-like humerus, the branches of 

 M'hich are long and styliform, the upper being joined to the occiput, 

 without distinct scapula between ; secondly, a strong curved cora- 

 coid ; and thirdly, a slender bone below the coracoid joint, which is a 

 rudiment of a fore-arm. The carpus is reduced to two elongate 

 bones, with a free interspace between them, the inner being the larger. 

 The pubic bone is composed of tkree processes : the longest and 

 broadest for the base of the fin, the shortest for the union with the 

 other pubic bone, and a third slender one for the attachment to the 

 humerus. 



There arc nineteen vertehrcc, eight of which iippear to belong to 



