Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 211 



pharyngeal process of the same bone, and from a tendinous line 

 that extends a short distance mesially from the process, along 

 the posterior edge of the proximal articular head of the fourth 

 epibranchial. None of the fibers of the muscle arise directly from 

 the latter bone. The muscle runs forward and mesially, and then 

 forward, having a curved mesial edge and terminating in a point 

 directed forward. It is inserted along the mesial edge of the 

 anterior half of the dorsal surface of the third infrapharyngo- 

 branchial, the surface of origin lying mesial to the ridge along the 

 middle of the dorsal surface of the bone, and extending almost to 

 its anterior end. The anterior end of the muscle lies ventral to 

 the transversus anterior. It is innervated by branches of a nerve 

 that arises from the second vagus, the same nerve innervating 

 also the obliquus of the second arch, as described above. 



No obliquus dorsalis could be identified on the fourth arch. 



The Transversus Dorsalis Anterior (Tda) forms, with the 

 obliqui of the second pair of arches, a single muscle-mass, as 

 already stated. Like the obliqui of those arches, it arises, on each 

 side of the head, from the dorsal surface of the proximal articular 

 head of the second epibranchial, its anterior fibers running for- 

 ward and mesially, its posterior fibers directly mesially, or mesially 

 and slightly backward. The ventral fibers of the muscle cross the 

 middle line of the head and are inserted on the corresponding 

 portions of the second epibranchial of the opposite side. The 

 muscle is thus much wider in the median line of the head, than at 

 its lateral ends, its rounded anterior edge reaching forward nearly 

 to the level of the anterior ends of the second infrapharyngo- 

 branchials. On its dorsal surface, in the middle line, there is a 

 longitudinal, sucker-like, tendinous membrane, which forms part 

 of the muscle and clasps, or is inserted on, the rounded inferior 

 surface of the posterior half of the parasphenoid. Into this mem- 

 brane, and also in part directly onto the parasphenoid, a large part 

 of the fibers of the muscle have their insertion, the surface of in- 

 sertion extending dorsally slightly beyond the dorso-lateral edge 

 of the parasphenoid, on each side, onto the adjoining edges of the 

 petrosal and basioccipital (Fig. 11). On the ventral surface of 

 the muscle a similar but much more delicate membrane attaches 

 the muscle to the inner surface of the skin of the roof of the 



