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Bashford Dean Memorial Volume 



(1910.1, p. 554) states: "The vertebral column is fused to the cranium quite firmly, so 

 that but slight articulation is possible between the two.'' On this point AlUs (1923, 

 p. 161) writes: 



In my specimens of Chlamydoselachus there is no continuity of the cartilage here, so far as 



I can determine from macroscopic examination. The opposing surfaces of the chondro- 

 cranium and first vertebra are closely appHed to each other, and there is but Httle movement 

 possible between them, but a certain amount of lateral movement is nevertheless possible, and 

 the two articular surfaces can always be separated without breakage of the cartilage. 



S.d.L. llcL.69 



a.ctis. 



Text-figure 33. 



A portion of the vertebral column (s 1.4) of Chhmydosehchus, in the 



region of the dorsal and anal fins, showing the transition from mono- 



spondylous to diplospondylous vertebrae. 



a.ch.s., annulation in the chordal sheath; hd.69, basidorsal no. 69; hv., basiventrals; d./., 



dorsal foramen; h:, interventral; n.yO and n.72, neuromeres 70 and 72 respectively; s.bd., 



supra-basi dorsal; s.d.I., supradorsal Ugament; v.f., ventral foramen. 



After Goodey, 1910.1, Fig. 12, pi. XLIV. 



The vertebral column of Chlamydoselachus is of a very simple elasmobranch type. 

 The best description is that of Goodey (1910.1), and I shall base my treatment mainly on 

 his account. There is a long central cylinder, which comprises the notochord together 

 with its enlarged sheath. Above the chordal sheath there is a series of cartilaginous 

 vertebral elements arching over the spinal cord. These elements, comprising the neural 

 arches or the dorsalia, are classified by Goodey, using Gadow's (I895j nomenclature, as 

 follows: basidorsals, interdorsals and supra-basidorsals, the last-named being segmented 

 oif from the apices of the basidorsals. Below the chordal sheath there is another series 

 of vertebral elements, the ventralia, consisting of basiventrals, interventrals, ribs, and 

 haemal spines in the caudal region. These various elements making up the vertebral 

 column are illustrated in Text-figures 30-33 inclusive. There is an elastic supradorsal 

 Ugament which extends from the cranium to a point just posterior to the dorsal fin. 

 This must greatly strengthen the column. 



There is no detailed account of the histological structure of the chordal sheath in 

 Chlamydoselachus, but in Heptanchus (Daniel, 1934, p. 48, and Fig. 52 reproduced as my 



