MUSTKLfTS L.T-VIS. 179 



lu^xt procodino' or aiitorior liil)inl nvrli. Tt sliould hero he 

 stated that there are in my eiiihryos, eoiitrary to (leo'enbaur's 

 statement (23^, p. 214) for the adult, two separate and distinct 

 npper ]al)ial cartilag-es, both lying in, or in relation to, the 

 laljial fold of the fish. The anterior cartilag-e hns no direct 

 relations to any of tlu^ nmscles of the fish."^ 



There are thus two pre-oral arches indicated in embryos of 

 Mustelns. In each arch there are what are considered by 

 (legenbanr as remnants of the cartilages of the arch, and. I 

 now further find not only muscles definitely related to one of 

 the arches, but also nerves that certainly might be considered 

 as the pre- and post-trematic l)ranches of each arch. The 

 nervus trigeminus would then be a nerve formed In' the fusion 

 of at least three segmental nerves, and the ramus maxillaris 

 superior trigemiui would ])rol)ably contain the pharyngeal 

 elements of all these nerves, in addition to containing, in its 

 proximal portion, certain of their pre- and post-trematic 

 elements. 



The rannis niandibularis of Mustelus, after giving off the 

 branch to the lal)ial fold above described, passes downward 

 and backward on to the lateral surface of the adductor man- 

 dibul^e, lying at first between that muscle and the ])()sterior 

 poi'tion of the muscle Add/3, and then becoming gradually 

 imbedded in, and entii'ely enveloped in, the single muscle 

 formed by the fusion of these two muscles. Continuing back- 

 ward and mesially in this ]iosition it separates into two nearly 

 e(|ual ])ortions. One of these two portions is proliably wholly 

 motor, and is the ramus ad musculum adductoris mandibula?. 

 It remains always in the interior of the muscle-mass, and 

 running backward and downward sends branches both to the 

 superior and inferior divisions of the muscle. Two branches 

 were sent through the muscle to its dorso-mesial corner, and 



' Gcgeiibaur in liis references to the labial cartilages of ^lustelus, and also 

 elsewhere, refers in the text l<) his fig. 2, Plate XII, as representing 

 Mustelns, but this figure, in the descripiion of the plates, is said to be of 

 Galeus — an evident typographical error, as Marshall and Spencer have already 

 pointed out. 



