138 MR. PJ. PHELPS ALLIS, JUN., ON 



third sub-group, of ten pores, dorsal to the outer buccalis canal 

 and postero-lateral to the point where that canal is joined by the 

 supraorbital canal. 



The second, or ventral group of inner buccalis ampullse has the 

 position of the group B"" of Cole's descriptions, and it also lies 

 between the two layers of the subepidermal membrane, about 

 midway between the median and lateral rostral processes. From 

 thei-e the tubules run postero-ventrally, internal to the tubules 

 of the dorsal buccalis ampullar, and open on the external surface 

 in a lonof line which begins at the point where the outer bviccalis 

 canal falls into the anterior one of the twohyomandibular canals 

 of Cole's descriptions and extends along tlie dorso-anterior edge 

 of the latter canal until it reaches the postero -ventral end of the 

 supramaxillary fold. Tiiere the line of the ampullary pores 

 turns dorso-anteriorly along the edge of the supramaxillary 

 fold, and so continues nearly to the median line. 



The outer group of buccalis ampullae is Cole's group B^, and it 

 lies ventral to the base of the lateral rostral process. The 

 tubules of these ampullae all run ventrally and pass internal to 

 the supramaxillary furrow. There two tubules separate from 

 the others, and running mesial to the external nasal aperture 

 open on the external surface immediately ventro-mesial to that, 

 aperture. The remaining tubules of the group pass postero- 

 lateral to the external nasal aperture, and open along the ventral 

 edge of the nasal portion of the naso-labial fold. These ampullae 

 and their tubules all lie internal to the inner layer of the sub- 

 epidermal membi'ane, but they are surrounded by delicate con- 

 nective tissues that would seem to represent the corresponding 

 laver of the corium. 



Closely related to the ampullary pores on the ventival surface of 

 the snout, there are several patches of small depi'essions which 

 are the external openings of little glandular structures that are 

 of epidermal origin and form little protuberances on the intoi^nal 

 surface of the epidermis, suggesting undeveloped or degenerate 

 ampullae. 



The subepidermal membrane in which, as above described, the 

 larger part of the ampullary tubules lie is formed by the outer 

 fibrous layer of the corium. The latero-sensory grooves, and the 

 calcified cartilaginous rings that partly surround and support 

 them, all lie external to this fibrous layer, as Wright (1884, 

 p. 263) says that the latero-sensory canals of embryos of Amiurus 

 also do to the corresponding layer in that fish. The membrane 

 passes external to the three rostral processes, and there encloses 

 a, median, three-sided space which lies between the three pro- 

 cesses. The membrane is here thick, because of the accumulation 

 of the enclosed ampullaiy tubules and sacs, and the inner layer 

 of the membrane is markedly reticulated, the meshes in the 

 membrane being traversed by the tubules of certain of the 

 ampullfe and by the nerves that supply the others. The median 

 portion of the three-sided space is filled with loose fatty con- 

 nective tissue, and the nervus ophthalmicus suj)erficialis of either 



