OSTEOLOGY. 295 



closely applied along the symphysis for some 40 mm., are not anchylosed, but 

 doubtless remain separate throughout life. The measurements of three adult 

 skulls and two smaller and more j-outhful examples, as well as those of the 

 type as given by Peters and Doria (1876) are tabulated on page 296. Thomas 

 (1888) gives dmiensions of two skulls in the British museum. 



Gervais (1877-'78) m his account of the osteology of this anuBal figures 

 two skulls. The first is shown m his Plate 9, fig. 1, of natural size, and is of 

 almost exactly the same dimensions as ]\I. C. Z. 12,415 given above. No sutures 

 are indicated and it is doubtless the skull of a nearly mature animal. Gervais 

 considered it the skull of a male. In his Plate 7, figs. 1-lb, are shown three 

 views of a larger skull, of natural size, which if correctly drawn, incUcate a larger 

 animal than either of the old examples here noticed. The greatest length of 

 the skull, as measured from these figures is 197 nmi.; ba.sal length, 187; palatal 

 length, 174 =t ; tip of rostrum to orbit, 129; least interorbital width, 19; great- 

 est width of brain-case, 57 ; anterior margin of orbit to temporal canal, 43 ; great- 

 est length of mandible, 153. 



The hyoid apparatus of the Proechidna appears to be still undescribed. 

 The larynx is situated far posteriorly on the throat and the hyoid bones are 

 few and small (Plate 2, fig. 7). The basihyal is relatively broad and bears at 

 each end on its anterior face a cephalic cornu of two pieces, the basal of which 

 probably represents a ceratohyal. The more distal piece is of about half the 

 size of the latter and tapers to a point which is connected by tissue with the 

 sides of the pharynx. No tympanohyal articulating the larynx with the skull 

 appears to exist. At the posterior face of each end of the basihyal, a large thjTo- 

 hj-al passes dorsally to the cephaUc cornu of the thyroid cartilage. The cricoid 

 cartilage joins the thyroid by a common median cartilage, though a faint trans- 

 verse line probably indicates the original separation of the portion proper to 

 each ring. The more ventral portions of thyroid and cricoid are bony. The 

 arytenoid processes are produced backward as a long tapering cartilage to the 

 dorsal end of the cricoid. Following the cricoid is a large, nearly complete 

 tracheal ring, succeeded by the trachea, which consists of some 18 or 19 carti- 

 lagmous pieces not quite complete dorsally. 



Vertebrae. — The vertebrae of the Proechidna have been well figured by 

 Gervais (1877-78) and their general character is as in the Echidna. The first 

 seven (cervicals) have a complete vertebral arch, fomied by the union of the 

 cervical rib with the transverse process and the centrum. In old indi\-iduals 

 these ribs become solidly fused with their respective vertebrae. Such true 



