147 
ventral to the root of the nervus profundus and running forwards by 
the side of the brain, emerges on to the surface of the face im- 
mediately in front of the dorsalmost portion of the basilaris muscle 
and therefore some distance in front of the eye, and below the pro- 
fundus nerve (O.8.P.). On the surface of the head it runs forward 
‘below the profundus for some distance and then divides into three 
branches: two anterior small ones which run over the anularis muscle 
and apparently supply it, and a third large branch which runs straight 
down to the front wall of the gular pouch and supplies the tbick 
muscles of that part of the sack wall. The nerve is therefore either 
wholly or mainly motor. The other conspicuous nerve (92) arises 
directly in front of the eye immediately below the origin (on the 
face) of the buccal nerve (B.N.). Its consists of at least two kinds 
of fibres—cutaneous sensory and lateralis. ‘The former supply the 
leaf-like (and probably the tentacular) sensory structures borne on the 
margin of the suctorial disc; the latter supply those few scattered 
neuromast organs situated on the anterior portion of the gular sac. 
The neuromast organs situated on the posterior lateral region of the 
gular sac are supplied by a “hyomandibular” branch of lateralis 
fibres (Hyo. Lat.). 
Mordacia mordax, V.C. 
Diagnostic Characters of the Genus and Species. 
The genus Mordacia (for figures see Puate 49) is distinguished, 
according to PLATE, Oaitey and others, by the following characters :-— 
a gular sac is not present at any stage of the animal’s life and the 
suctorial funnel is not more developed than in Petromyzon; two dorsal 
fins exists, the former of which is much smaller than the hind and the 
hind fin is confluent with the tail fin; the anus is situated at the level of 
the hind end of the large posterior dorsal fin; the lip border is beset with 
small tentacle-like cirri only; maxillary teeth are two in number, each 
being situated dorsally and slightly laterally and consisting of a triang- 
ular plate bearing three curved hooks (fig. 31); the disc teeth are 
radially arranged. Mordacia mordax is, according to Piars, distin- 
guished from the other two species named by him by the following 
characters: the anterior pair of “tongue” teeth are broad plates 
- bearing numerous small spines (fig. 34) and there is a complete circle 
of disc teeth consisting of basal plates bearing from 1—4 spines, the 
three near the mid-dorsal line bearing one spine only (my fig. 31 
shows seven 1-spined teeth). 
10* 
