— 49 — 



bony ascending process of the parasphenoid, this line of tissue edging the anterior edge of the plate 

 of cartilage that represents the ventral portion of the proötic and then passing downward along the 

 external surfaee of that cartilage. From the niesial edge of the bridge of tissue, and from the mem- 

 branous cranial wall posterior to it, another line of tissue descends, passing along the internal surfaee 

 of the proötic cartilage. Between the two descending lines of tissue, anteriorly, and between the 

 proötic cartilage and the internal line of tissue posteriorly, a space is left, which, in the 45 mm spec- 

 imens, is filled with fat globules and loose connective tissue. This space lies immediately beneath 

 the trigemino-facialis Chamber, and its dorsal wall ossifies to form the thin bony floor of that Chamber. 

 In its anterior portion the space is teil, extending from the floor of the trigemino-facialis Chamber 

 downward beyond the line of origin of the mesial process of the proötic; that process here being 

 wholly of membrane, and rising perpendicularly from the niembranous mesial wall of the space. 

 Slightly posterior to this. in those sections that cut through the trigeminus foramen, the fat space 

 separates into dorsal and ventral limbs. The dorsal limb continues backward immediately beneath 

 the floor of the trigemino-facialis chamber and extends to the bind end of that chamber. The ventral 

 limb extends backward to the hind end of the proötic cartilage, lying always opposite the line of origin 

 of the membranous portion of the mesial process of the proötic, but passing ventral to the cartilaginous 

 portion of that process and there occupying the dorso-lateral corner of the myodome. The lateral 

 wall of the dorsal limb of the space is always formed of membrane or of membrane bone. The lateral 

 wall of the ventral limb is always of cartilage, this limb of the space lying in a wide and shallow groove 

 on the inner surfaee of the proötic cartilage, the dorsal edge of the groove being marked by a sharp 

 edge or ridge. 



This space in the proötic evidently has some special morphological significance, for, although 

 not evident in the adult Scorpaena, it quite certainly has its homologue in an important vaeuity found 

 in the proötic of the adults of certain other teleosts, as will later be shown when describing the myodome 

 in Gadus. It may be referred to as the proötic vaeuity. The mesial wall of the anterior part of the 

 vaeuity is, in the 45 mm Scorpaena, a direct ventral continuation of the mesial wall of the trigemino- 

 facialis Chamber, the lateral wall of this anterior part of the vaeuity being similarly related to the 

 lateral wall of that chamber. 



Close to the anterior end of the proötic vaeuity, in the 45 mm Scorpaena, the ramus palatinus 

 facialis pierces the membrane that later ossifies as the mesial process of the proötic, near the base 

 of that process, and passing internal to the anterior edge of the proötic cartilage enters the myodome. 

 The nerve arises from the intracranial communis ganglion, and does not in any part of its course enter 

 the trigemino-facialis chamber. In the intracranial part of its course, it lies along the cerebral surfaee 

 of a membranous portion of the cranial wall, imbedded in loose connective tissues, these same tissues 

 also enclosing, mesially, the intracranial portion of the trigemino-facialis ganglion, and being prolonged 

 dorsally as part of the cerebral wall of the labyrinth recess. This tissue may therefore represent the 

 tough glistening membrane that, in Amia, forms the lateral bounding wall of the cranial cavity in 

 the pituitary region, though it seems more probable that that membrane is represented, in Scorpaena, 

 in the membrane that forms the mesial wall of the trigemino-facialis chamber. Following Sagemehl, 

 I ('97) formerly considered the tough glistening membrane of Amia as a specially developed portion 

 of the dura mater. My present work leads nie to aeeept this conclusion only with the proviso that the 

 dura mater is itself a differentiated portion of the membranous tissue that primarily forms the en- 

 closing capsule of the central nervous System. 



Zoologica. Heft 57. 7 



