(î70 E. PH. ALLIS, 



On leaving bone 1 the main infraorbital canal enters and traverses, 

 somewhat transversely, bone 2 ; at about the middle and thickest part 

 of which bone the dorsal end of the so-called hyomandibular canal 

 usually anastomoses with the main infraorbital. In one specimen, 

 however, this anastomosis took place between bones 1 and 5, a simple 

 dendritic system arising from the main infraorbital as it traversed 

 bone 2. A primary tube always arises from the hyomandibular canal 

 near the point of anastomosis with the main infraorbital, and it is 

 doubtless the tube of the double system that should normally there 

 be formed. 



Having left bone 2 the canal passes downward behind, and for- 

 ward below, the eye, there being enclosed in a series of ossicles, as 

 Bridge and Collinge have both stated, these ossicles lying in the 

 connective tissues at a certain distance below the skin, and not im- 

 mediately beneath the skin as they do in the supratemporal region. 



Anterior to the eye the canal is said by Collinge to anastomose 

 with the anterior end of the supraorbital canal, but I have failed to 

 find any trace of such an anastomosis in either of the several dis- 

 sections made. The supraorbital canal, in all these several specimens, 

 ends in a terminal dendritic system that lies in the roof of the nasal 

 cavity some distance dorsal to the main infraorbital canal. The latter 

 canal here runs directly forward, without bend or break, lying in the 

 loose connective tissues beneath the skin on the ventral surface of 

 the snout, and giving ofi" a number of primary tubes each of which 

 opens by several pores on the ventral surface of the long spatula- 

 shaped snout. Whether the canal was here enclosed in "a series of 

 canal bones", as Collinge states, or not, I did not attempt to definitely 

 determine, but it seemed to be in large part, a purely membranous 

 tube. Collinge says that the canal here passes "forwards and in- 

 wards towards the parasphenoid and continues along its lateral border" ; 

 and that as it approaches "the anterior portion of the rostrum the 

 diameter of the canal becomes less, diverges laterally, and passes 

 around the anterior border, joining with its fellow half of the opposite 

 side in the median line". The bone here referred to as the para- 

 sphenoid must either be the vomer of Bridge's descriptions, or the 

 "azygous splint" that Bridge says (p. 692) "would appear to be the 

 homologue of the anterior parasphenoid described by Parker as ex- 

 isting in Bana pipiens''\ This azygous splint of Polyodon, it is to be 

 noted, lies on the ventral surface of the snout considerably anterior 

 to the mouth cavity, while the anterior parasphenoid of Bana lies in 



