— 36 — 



is traversed by the main infraorbital canal, and lodges one organ of that canal. The hind corner of 

 the bone may be either sharp or rounded, and as it forms a slight eminence in the dermis may be 

 considered as the last spine of the lateral row. The occipito-supraclavicular ligament is inserted on 

 the internal surface of the supraclavicular, in the usual manner. 



LATERAL SURFACE OF THE BRAIN CASE. 



The lateral surface of the brain case of Scorpaena is inclined at an angle of 45 °, approximately, 

 to the horizontal plane. Its ventral half is crossed transversely, from above downward and back- 

 ward, by the elongated, fusiform and prominent swelling of the bulla acustica. Anterior to this 

 swelling, there is, on the ventral half of the lateral surface of the brain case, a depressed region which 

 lies on the proötic and parasphenoid. The posterior and larger part of this depressed surface is filled 

 by and gives attachment to a large tough päd of connective and muscular tissue, which is continuous, 

 across the middle line, with a similar päd on the other side, the two together representing the anterior 

 transversus dorsalis muscle. The lateral border of the päd of either side gives attachment to a short 

 rnuscle which has its insertion on the epibranchial of the second arch, and is the obliquus dorsalis of 

 that arch; the two short muscles, one on either side, together with the intervening päd, forming a 

 single mass, as in Scomber. The posterior transversus dorsalis is a thin band of muscle extending 

 from the third and fourth epibranchials of one side transversely across to the corresponding bones of 

 the other side. 



Anterior to the anterior transversus dorsalis, the infrapharyngobranchial of the first arch is 

 attached to the side wall of the skull; and, anterior to that element, the posterior portion of the 

 adductor arcus palatini has its origin. The surface of origin of this latter muscle begins immediately 

 ventral to the trigeminus opening of the trigemino-facialis chamber, there lying partly on the proötic 

 and partly on the ascending process of the parasphenoid. From there it extends downward and for- 

 ward along the anterior portion of the latter process, and then turns directly forward, occupying a 

 depressed region along the lateral edge of the body of the parasphenoid and extending forward across 

 the orbit to the antorbital process of the skull. From this long surface of origin the broad and relatively 

 thin muscle extends latero-ventrally and has its insertion mainly on the palato-quadrate arch, as will 

 be later more fully described, its posterior portion, however, having its insertion on the inner surface 

 of the thin flange of bone that forms the anterior edge of the hyomandibular. The muscle thus acts 

 in part as an adductor hyomandibularis, but it is widely and wholly separate, both at its origin and 

 insertion, from the latter muscle, properly so-called. 



Immediately dorsal to the anterior end of the bulla acustica is the opening usually called the 

 facial foramen, but this so-called foramen is, as in Scomber, the facialis opening of the trigemino- 

 facialis chamber. Posterior to this opening, and extending across the lateral surface of the skull to 

 its hind edge, there is a large, shallow, and, in certain specimens, distinctly pyramidal depression 

 which lies on the proötic, opisthotic and exoccipital bones. The depression is subtriangular in outline, 

 the base of the triangle being formed by the dorsal edge of the anterior portion of the bulla, the posterior 

 edge by a part of the postero-lateral edge of the skull, and the antero-dorsal edge by a low ridge 

 that runs downward and forward across the lateral surface of the brain case, approximately in the 

 line prolonged of the opisthotic process of the suprascapular. The center of the depression, some- 

 what pointed in certain specimens, lies within the arch of the external semicircular canal, ventral 

 to that canal, and in this the depression corresponds to the subtemporal fossa of Sagemehl's 



