64 



height, and its base extends from the foramen magnum to the nasal bone. The lateral ridges 

 formed by the cranial parapophyses, viz. the postfrontals and mastoids, are almost equally 

 developed horizontally. The coracoids are much expanded inferiorly, they meet along an 

 extensive symphysial surface, and form a large and equable concavity directed backwards. 

 The ulna is large and perforated ; but the radius is enormously developed and meets its 

 fellow below and behind the coracoids, like a second arch. The epicoracoid consists of two 

 pieces ; the upper expanded portion is attached to the coracoid, the lower elongated and 

 slender portion adheres to the posterior margin of the radius ; it is of very great length. The 

 pubic bones are attached to the lower united ends of the radius. The terminal anchylosed 

 bodies of the caudal vertebrae send out a horizontal ridge on each side. The number of 

 abdominal vertebrae is 20 ; that of the caudal vertebrae is 28, =48. 



Mus. South. 



255. The skull of the Cock-fish (Argyreiosus Vomer, Cuv.). 



The suborbital bones and the left half of the maxillary and mandibular arches have been 

 removed to show the proper bones of the cranium, the hyoid, and the branchial arches. The 

 silvery pigment is laid upon both the inner and outer sides of the large suborbital, the oper- 

 cular, the subopercular and interopercular bones ; but not upon the preopercular bone. 



The stylohyal is articulated to the interspace or ligamentous joint between the epitympanic 

 and the mesotympanic, and it is connected by a strong fascia to the pretympanic ; it articulates 

 at an acute angle with the epihyal, which is a flat triangular bone : the ceratohyal is a larger 

 and broader plate. The basihyals form a bony cell, convex forwards, supporting, above, the 

 glossohyal, which is shagreened with minute teeth ; and having articulated to their posterior 

 concavity, the urohyal, which expands into a very broad, thin triangular plate, whose base is 

 attached by ligament to the coracoid symphysis. 



The first branchial arch sends forwards from its anterior concave border a series of com- 

 pressed, long and narrow triangular ossicles dentated on their inner border : these ossicles are 

 nearly as long as the gill-filaments that project from the opposite border. The inner side o 

 this branchial arch supports a series of tubercles minutely shagreened, and fitting into the 

 intervals of a similar series from the contiguous side of the next arch. No anterior processes 

 are sent off from the second or succeeding arches ; the fifth or pharyngeal arch supports a long 

 inequilateral triangular patch of short villous teeth. 



Presented by Prof. Owen, F.R.8. 



256. The skeleton of the Arthritic Chaetodon (Platax arthriticus). 



Like all deep-bodied fish, it is remarkable for the length of the neural and haemal spines, 

 and of the dermal spines supporting the dorsal and anal fins ; but it is peculiarly distinguished 

 by the development of masses of osseous matter at different parts of the skeleton. The 

 anchylosed spines of the cranial vertebrae form a large compressed triangular piece like the 

 crest of a helmet, thick and convex in front, sharp-edged behind. A second smaller mass of 

 bone is developed at the summit of the first interneural spine. The neural spines of the 

 second, fourth, sixth and eighth caudal vertebrae are similarly developed, and the third 

 caudal spine in a slighter degree. The base of the first interheemal spine swells into a large 



