— 47 — 



anterior to that wall. A much smaller but siinilar web of bone may separate the recess into dorsal 

 and ventral portions, the facialis and palatinus foramina leading, in such cases, froni the ventral 

 portion of the recess, and the trigemiuus and profundus foramina from its dorsal portion. The recess 

 lodges the profundus ganglion and also the lateralis and communis portions of the trigemino-facialis 

 ganglionic complex. The recess can accordingly be called the trigemino-facialis recess, although, 

 as already stated, geniculate recess might be a more proper designation. 



The canal for the ramus palatinus facialis thus perforates, in Scorpaena, the base of the mesial 

 process of the proötic and does not enter the trigemino-facialis Chamber in any part of its course; 

 and this is the condition found also in the Characinidae (Sagemehl, '84 b, p. 65) and Cyprinidae 

 (Sagemehl, '91, p. 558). In Scomber, on the contrary, the nerve first enters the trigemino-facialis 

 Chamber and then pierces the proötic to enter the myodome (Allis '03). In Trigla Lepidotrigla and 

 Dactylopterus, as will be later shown, the nerve also first enters the trigemino-facialis Chamber, but 

 instead of then piercing the proötic by a separate canal, as in Scomber, it simply issues by the trige- 

 minus opening of the chamber and so enters the orbit. In Menidia, the nerve is said by Herrick 

 ('99, p. 176) not to enter the myodome (sub-cranial canal), butto run ,,along the outer side of the 

 canal, not the inner"; thus apparently being either as in Scomber, or as in Trigla Lepidotrigla and 

 Dactylopterus. 



Immediately posterior to the trigemino-facialis recess, the labyrinth recess begins, and in 

 that recess, on the internal surface of the proötic and immediately dorso-postero-lateral to the 

 trigemino-facialis recess, there are two adjoining depressions, the anterior one lodging the ampulla 

 of the anterior semicircular canal, and the posterior one the ampulla of the external canal. Ventro- 

 mesial to these depressions, and immediately posterior to the ventral portion of the trigemino- 

 facialis recess, a large and deep longitudinal groove begins, and, extending backward to the bind 

 end of the proötic, immediately dorsal to the base of the postpituitary portion of the mesial process 

 of the bone, forms the anterior portion of the saccular groove. The bottom of this groove is thin, 

 and this part of the proötic forms, on the outer surface of the skull, the anterior part of the bulla acustica. 



The conditions in the proötic region of 45 mm specimens, examined in serial sections, must 

 now be considered. In these specimens, the basisphenoid bone is just beginning to develop, and lies 

 immediately posterior and ventral to the posteriorly directed dorsal end of the basisphenoid cartil- 

 age. Excepting only this little bone and cartilage, the floor of the cranial cavity is, at this age, wholly 

 membranous from its anterior end back to the abducens foramina. Immediately posterior to the 

 abducens foramina, the cranial floor is formed by a horizontal bridge of cartilage which corresponds 

 exactly, in extent and position, to the bony bridge formed by the united mesial processes of the proötics 

 of the adult Amia. But the saccus vasculosus lies, both in these 45 mm specimens and also in the 

 adult Scorpaena, on the dorsal surface of this proötic bridge, while in Amia it lies (Allis, '97 a, pp. 494 

 und 505) ventral to that bridge. As the bridges in these two fishes are unquestionably homologous, 

 this difference in the position of the saccus, if the sacci also are homologous, must be caused by its 

 being, in Scorpaena, pulled out from beneath, and lifted up above the bridge, by the greatly 

 devcloped hypoaria; the saccus thus being pulled out of the myodome and so losing all relation to 

 that canal. 



Those parts of the mesial processes of the proötics of the adult Scorpaena that lie anterior 

 to the abducens foramina are thus not preformed in cartilage, and must accordingly be developed 

 wholly in membrane, as I was led to conclude, in an earlier work ('97), that they must be in all teleosts. 



