ON THE MEMBRANOUS LABTRINTHS OP CERTAIN SHARKS. 407 



EXPLANATION OF PLATE 39. 



Fig. 1. Skull oi Biziura lobata, side view. 



^. = lachrymal. ??2.r. = maxilla. jj. = nasal. jpa. = palatine. iJ.o.'p.'=- 

 postorbital process. z;._/.= temporal fossa, g.^^ quadrate. w.=Tonier. 

 Fig. 2. Pelvis of Biziura lobata, dorsal aspect. 



a.=acetabulum. «7.=ilium. zs.=ischium. p. = pre-acetabular 

 ilium, joi. =pubis. s.s. = synsacral crest. 

 Fig. 3. Portion of right leg of Biziura lobata, outer aspect. 

 /. = femur. /S.=fibula. p?;. = patella. z'. = tibia. 



On the Membranous Labyrinths of certain Sharks. 

 By Charles Stewart, T.E.S., P.L.S. 



[Bead 16th November, 1905.] 

 (Plate 40.) 



The admirable monograph on the ox'gans of hearing of the 

 Yertebrata by Prof. Eetzius * leaves little or nothing that one 

 would wish to add to the account of the forms therein treated ; 

 but having had the opportunity of examining some not dealt 

 with, in that work, it seems desirable to give some record of their 

 structure. 



One cannot but recognize that features apparently most trivial 

 may prove useful in helping to show the real affinities of an 

 organism, and occasionally the solution of the more difficult 

 question of the function of a structure may be suggested, 

 when such a structure is found to be possessed by forms 

 dwelling in a like environment that by other features have had 

 their affinities differently interpreted. 



NoTiDANUS GRiSETJS. Paui. JSTotidanidss. 



In this Shark the utricle presents the ordinary elasmobrauch 

 features as figured by Eetzius and others, being divided into 

 two portions not directly communicating with one another and 

 with their walls completely separate. In spite of the fact that 

 Eetzius reserves the name utricle for the anterior of these, and 

 calls the other posterior canal, I propose speaking of them here 

 as utriculus anterior and utriculus posterior ; for a comparison 

 with the utricle of e. g. Teleostea leaves no doubt that they are 

 portions of that chamber (I. c. p. 218). 



The anterior utricle has no direct opening into the saccule, 

 but communicates with it indirectly through the recessus utriculi. 

 * ' Das Gehororgan der Wirbelthiere,' Bd. i. (1881). 



