. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 431 Scylliura, Pristiurus, Mustelus, Galeus, and the two Batoids, Rhynchobatus and Syrrhina. Van Bemmelen adds Acanthias, Squatina and Heptanchiis to Müller's list. In Acanthias, however, it is not the dorsal caecum, but the mucous membrane of the spiracle itself, that is bound to the auditory cartilage. The attachment, moreover, is eifected below and not above the post- orbital Fig. 2. Scyll ium cauicula. Transverse section of head, showing the relations of the spiracular casca. VC position of ventral spiracular cje
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 431 Scylliura, Pristiurus, Mustelus, Galeus, and the two Batoids, Rhynchobatus and Syrrhina. Van Bemmelen adds Acanthias, Squatina and Heptanchiis to Müller's list. In Acanthias, however, it is not the dorsal caecum, but the mucous membrane of the spiracle itself, that is bound to the auditory cartilage. The attachment, moreover, is eifected below and not above the post- orbital Fig. 2. Scyll ium cauicula. Transverse section of head, showing the relations of the spiracular casca. VC position of ventral spiracular cjecum; ch ceratohyal ; cbr first ceratobranchial; m mouth cavity; md mandible; pq palatoquadrate cartilage; sp external aperture of spiracle; dc dorsal spiracular cacum ; pos post-orbital blood-sinus; hsc horizontal semi- circular canal; cc cranial cavity; v vestibule of ear; hm hyomandibular cartilage. Projecting inwards and forwards from the inner wall of the spiracle, near its pharyngeal opening, is another diverticulum, much shallower in extent and with a wide mouth. It is situated below the level of the pre-spiracular cartilage, and immediately in front of the proximal end of the hyomandibular. It is bounded anteriorly by the levator maxilkTe superior is muscle, and posteriorly by the anterior sur- face of the hyomandibular cartilage and the inferior post-spiracular ligament. The blind extremity of this ventral ca3cum is separated only by the thickness of its mucous membrane from the orbital blood- sinus. Van Bemmelen claims to have discovered a "Ventraler Spritz- lochfollikel" which has exactly the relations of this ventral caecum, except that it is united with the spiracular wall by a short stalk with a narrow or no lumen. On comparing Mustelus, in which the ventral spiracular caecum is very well shown, with Z y g ae n a and C a r c h a r i a s , the pharyngeal. Please note that these images are extracted from scanned page images that may have been digitally enh
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