530 PROP. T. W. BRIDGE ON THE 



of the anterior chamber of the air-bladder are in contact, often 

 over a considerable area, with the superficial skin behind the 

 pectoral girdle. 



Notopterus is by no means the only Teleost in which the 

 existence of cranial fontanelles, more or less closely associated 

 with the auditory organ, has been recorded. Nevertheless, tbe 

 position of these vacuities, and their precise relation to the 

 membranous labyrinth, exhibit a wide range of variation in 

 different Teleosts. 



In Notopterus, as we have seen, the fontanelles are situated on 

 the upper surface of the hinder part of the skull and immediately 

 dorsad to the auditory capsules. 



According to Stannius (11. p. 170) cranial fontanelles essen- 

 tially similar to those of Notopterus exist also in Hyodon 

 claudulus. 



In the Herring {Glupea Tiarengus, L.) " the ventro-external 

 surface of the sacculus lies over a membranous fenestra of the 

 skull-wall, situated between the exoccipital, basioccipital, and 

 prootic bones, and described by several authors as a foramen 

 ovale ; the sacculus-wall is here separated from the mucous 

 membrane of the mouth by this membrane only " (Hidewood, op. 

 cit. p. 38). 



In referring to certain of the Macruridse, Stannius {op. cit. 

 p. 170) * states : — " Bei Lepidoleprtcs trachyrhynchus t findet 

 sich seitlich am Hinterkopfe iiber dem oberen Ende der Kiemen- 

 spalte eine trichterformige von diinner Haut gesschlossene Grube, 

 welche in den zur Aufnahme des G-ehororganes bestimmten 

 Theil der Schedelhohle hineinragt. Zwischen der Innenflache 

 ihrer Haut und dem Labyriuthe liegt eine faserig-gallertartige 

 Substanz." Similar fontanelles are said to be present in L. coelo- 

 rhyncJius, but not in X. norvegicus. 



Tbe skin-covered fontanelles on the postero-superior surface 

 of the skull of Mormyrus somewhat resemble those of Lepido- 

 leprus, except that immediately beneath the external skin there 

 is a perfectly free and very thin lamina of bone which partially 

 covers each f ontanelle (Stannius, op, cit. p. 170 J). Fontanelles, 



* On the authority of Otto, Tiedemann u. Treviranua' Zeitschrift f. Physiol., 

 Bd. ii. S. 86 



t =.Macrurus trachyrhynchus, Risao. 



\ Apparently on the authority of S. Heusinger, Meckel's Archiv f. Anat. u. 

 Physiol. 1827, Bd. i. S. 324. 



