178 TRIGtlD^. 



V. Twenty-two inches long -. stuifed. From the Collection of the 



Zoological Society. 

 w. Adult : skeleton. From the Haslar Collection. 

 X. Half-grown. Presented by the Zoological Society. 



Skeleton. — If the skull of Cottus gobio, or of one of the allied spe- 

 cies, were imagined to be more strongly depressed and more elongate, 

 it would be that of a PJatycephalus. In the present species, the bones 

 of the upper surface of the skull, of the infraorbital ring, and of the 

 opercular apparatus form one triangular plane, without any conspi- 

 cuous ridges. The maxiUary bone is of moderate extent, obliquely 

 truncated posteriorly ; the intermaxillary is much shorter, and has 

 the posterior processes rather feeble ; the descending branch widens 

 behind. The mandibula is long, veiy low, nearly styliform, without 

 any conspicuous muciferous channel. The vomer and the palatine 

 bones are broad and flat ; the fonner is rounded anteriorly. The 

 turbinal bones are very thin, not armed. The infraorbital bones are 

 oblong, and there is a smooth I'idge fi'om the centre of the praeorbital 

 to the angle of the prreoperculum. The prisorbital has several low 

 ridges besides, radiatiag from a centre, and two or three terminating 

 in small sjjines. The posterior infraorbital bone is broadly attached 

 to the praeoperculum ; two small postorbital hones close the orbit 

 posteriorly. The orbit itself is relatively small, its longest diameter 

 equalling the width between the orbits. The prseopercular hmbs 

 form together a somewhat acute angle, armed with two spines ; each 

 limb has a distinct muciferous channel. The operculum has two 

 slight ridges, terminating in veiy small spines ; the upper one is the 

 strongest, visible externally and internally. The ethmoid forms part 

 of the upper surface of the skull to between the orbits, the frontal 

 bones being separated from each other. The space between the 

 orbits is quite flat, as is the crown, — the longitudinal ridges which 

 are seen in other species being scarcely visible. The basisphenoid is 

 flat, rather broad, A^ithout ridges or grooves. The glossohyal is broad, 

 triangTilar, with the top of the triangle obtuse and pointing back- 

 wards. The form of the urohyal corresponds with the general con- 

 figuration of the head, the vertical ridge being vei-y low. 



The bones of the humeral arch, above the coracoid, are exceedingly 

 short. The situation and the form of the pubic bones do not ma- 

 terially differ from the same bones in Cottus or Trigla* : in the 

 three genera they are attached to the coracoid bones, and the fins are 

 therefore traly thoracic, and not abdominal. In each pubic bone of 

 the three genera, two axes can be distinguished, to which two 

 stronger ridges correspond ; the axes converge towards the insertion 

 of the ventral rays : — 1. A longitudinal axis, obliquely directed out- 

 wards : the anterior symphysis of the bones and the junction with the 

 coracoid are situated at the anterior end of this axis. 2. A horizontal 



* A single glance at the skeleton of Plafycephalus shows that Prof. Kaup, in 

 callmg the ventral fins of these fishes abdominal, has merely consulted their ex- 

 ternal appearance, and that the removal of Plafi/ccphatus from this family indi- 

 cates rather apetitio principi/, than the truth of his system. 



