THE CHONDROCKANIUM OF LEPID0STEU8. 247 



«liows, on the dorsal surface of the otic capsule, a marked depres- 

 sion, which corresponds to that portion of the sulcus longi- 

 tudinalis of the 149 mm. specimen that lies posterior to the ridge 

 of the anterior semicircular canal. This supraotic depression 

 opens posteriorly, across the posterior portion of the ridge of the 

 lateral semicircular canal, between that ridge and the ridg-e of the 

 posterior semicircular canal, on to the lateral surface of the chondro- 

 •cranium, and a slight depression leads from its dorso-mesial edge 

 a,cross the ridge of the posterior semicircular canal into a depres- 

 sion which lies postero-mesial to the latter ridge, between that 

 ridge and the bounding edge of the foramen magnum. This 

 latter depression is called by Veit the fossa supratemporalis, and 

 it corresponds to the postero-ventral prolongation of the snpra- 

 temporal groove of my descriptions of Scomber (Allis, '03). 

 There is in tliis embryo no epiotic process in any way com- 

 parable to that in the 149 mm. specimen, but the basal portion 

 ■of that process must be I'epresented in the summit of the ridge 

 of the posterior semicircular canal, for, in my 80 mm. specimen of 

 this fish, I thei-e find the epiotic already I'epresented by a thin 

 layer of perichondrinl bone. The strongly developed epiotic 

 process of the 149 mm. specimen must, therefore, have been 

 formed by the addition, to this perichondrial bone, of bone of 

 membran e ori gin . 



The so-called crista parotica of this embryo is said by Yeit 

 ('11, p. 168) to be a ridge which forms an anterior prolongation 

 of the ridge of the lateral semicircular canal (''springt in ihrer 

 Fortsetzung eine scharfe Leiste lateralwai'ts vor "), and it ends, 

 •anteriorly, at the summit of the postorbital process. The a,nterior 

 portion of the ridge is said to be perforated by a canal which 

 lodges the recessus dorsalis spiracularis, this part of the ridge 

 thus having no relations whatever to the ridge of the lateral 

 ■semicircular canal. The posterior portion of the crista is said 

 to form the dorsal edge of a small oval depression which 

 apparently occupies the full width of the ventral surface of the 

 ridge of the lateral semicircular canal, a,nd Veit calls this entire 

 depression the articular facet for the hyomandibula. 



In a 20 mm. embryo of this fish, examined in serial transverse 

 •sections, I find a longitudinal depression which has exactly the 

 position of the so-called facet for the hyomandibula of Veit's 

 20^ mm. embryo, but the hyomandibula, which is thin, ai^ticu- 

 lates with the dorso-lateral quai'ter only of this depression, there 

 lying immiediately beneath the spheno-pterotic ridge (Veit's 

 crista pai'otica). The ventro-mesial edge of the depression is 

 formed by a slight ridge, which gives insertion to the adductor 

 hyomandibularis, this ridge forming the dorsal edge of a groove 

 which lies between it and the bulla acustica and lodges the vena 

 jugularis. Between this slight ridge and the hyomandibula 

 there is a large lymph vessel which, at the hind edge of the 

 -adductor hyomandibularis and anterior to the levatores arcuum 

 'branchialium, separates into two parts, one running ventrally 



