48 



sending inwards a process from the inner surface, which meets and coalesces with that of the 

 opposite side, and is continued downwards as a haemal spine. The pleurapophyses are very 

 slender, and are appended to the extremities of the parapophyses. The interneural and der- 

 moneural spines form three groups, which are the bases of as many dorsal fins. The inter- 

 haemal and dermohaemal spines are in two groups, which support the two anal fins : the an- 

 terior group extends forwards beneath the abdomen in advance of the caudal region of the 

 vertebral column. The number of abdominal vertebrae is 20 ; that of the caudal vertebrae is 

 34 : total 54. 



Presented by James Syme, Esq. 



177. The skull of a Haddock (Merlangus aglefinus). The suborbital and supra- 



temporal dermal bones are preserved in this skull, but the hyoid and scapular 

 arches are wanting. The bones are indicated by numbers according to those 

 in Table I. Presented by Sir B. C. Brodie, Bart., F.R.8. 



178. The cranium, wanting the left coracoid, of a Haddock (Merlangus ceglejlnus}. 



Hunterian. 



Family Pleuronectida. Flat-fishes. 



179. The skeleton of the Plaice (Pleuronectes Platessa, Linn.; Platessa vulgaris, 



Cuv.). 



Like other fishes of the present family, it is remarkable for the departure from symmetry 

 in the bones of the head. In the present instance only one orbit is completed, and both eyes 

 are on the right side of the head. The teeth, on the other hand, are chiefly developed on 

 the left side ; they form a regular curvilinear series of about twenty in number, shaped like 

 incisors, in the left premaxillary ; and there is a similar series of about thirty teeth in the left 

 premandibular bone : only three or four small and ill-shapen teeth are developed in the right 

 premaxillary and right premandibular. The interneural and dermoneural spines begin to be 

 developed above the frontal bone, and are continued without interruption to near the base of 

 the tail, and they are of great length : there is a similarly uninterrupted series of bony inter- 

 haemal and dermohaemal spines in the caudal region of the trunk : the number of these deve- 

 lopments of the dermal skeleton is nearly twice that of the corresponding spines of the endo- 

 skeleton to which they are attached. The proportions and relative positions of the parapo- 

 physes and pleurapophyses in the abdomen much resemble those in the Cod-tribe : the haemal 

 arches are formed by special processes or divisions of the parapophyses, the external portions 

 of which continue to project outwards, as independent transverse processes, along about the , 

 anterior half of the caudal region, gradually subsiding and disappearing there. The number 

 of abdominal vertebrae in this skeleton is 13 ; that of the caudal vertebrae is 31 : total 44. 



Purchased. 



