LABIAL CARTILAGES OF RAIA CLAYATA. 
101 
in Raia vomer; this end of the labial of Raia clavata 
simply lying in dense connective tissues of the region, and 
the corresponding end of the nasal-flap cartilage lying upon 
and being firmly bound to it. On each side of the head the 
ventral edge of the posterior wall of the nasal capsule was 
partly membranous, and in this membrane there was a narrow 
and independent strip of cartilage. In the mesial wall of the 
capsule, near its ventral edge, there was a hiatus closed by 
membrane. One or more branches of the nervus trigeminus 
perforated the cartilage between the hiatus and the edge of 
the capsule. 
The nasal latero-sensory canal was so named by G-armaii 
(1888) in his descriptions of these fishes, and is the antorbital 
portion of the main infraorbital canal of my descriptions of 
Mustelus (Allis, 1901). Running mesial ly across the external 
surface of the musculi adductor mandibulae and levator labii 
superioris, this canal reaches the lateral edge of the lateral 
portion of the labial cartilage immediately anterior to the 
point where that cartilage assumes a position parallel to the 
external surface of the head. The canal then crosses the 
external surface of this portion of the labial and reaches its 
mesial edge, where it continues onward and reaches and 
traverses the narrow neck of cartilage that connects this 
lateral portion of the labial with its mesial portion. Having 
reached the mesial portion of the labial the canal turns 
abruptly posteriorly (orally) and crosses the external, surface 
of this part of the labial, lying close to its lateral edge. 
When the canal reaches the postero-mesial edge of the labial 
it traverses the incisure in the mesial edge of the nasal-flap 
cartilage and then turns abruptly antero-mesially along the 
postero-mesial edge of the labial ; and continuing in that 
direction it joins its fellow of the opposite side in the median 
line to form the median canal of Harman’s descriptions. 
The canal lies internal to the nasal-flap furrow, and internal 
also to the nasal-flap cartilage, and in no part of its course 
does it enter any part of the nasal flap. It lies everywhere 
external to the labial cartilage and is firmly attached to 
