350 Bashford Dean Memorial Volume 



(Text'figure 20), quite as readily as from teeth like those of Ctenacanthus clar\i (Text' 

 figure 19), Cladodus acutus Ag. (Text'figure 18) and Cladoselache fyleri (Text'figure 17), 

 which they more nearly resemble. 



THE ENDOSKELETON 



The most comprehensive studies of the endoskeleton of Chlamydoselachus are those 

 of Garman (1885.2), Deinega (1909 and 1923), and Goodey (1910.1). In addition, Giinther 

 (1887) described the skeleton of the claspers; Braus (1902) that of the paired fins; Fiir' 

 bringer (1903) and Garman (1913) the visceral skeleton; while Allis (1923), using material 

 supplied by Dr. Bashford Dean, described the skull. Deinega's first (1909) paper is 

 in Russian, but his original figures are reproduced in his later (1923) paper which 

 is in German. 



As in selachians generally, the endoskeleton (excepting the notochord) of Chlamy- 

 doselachus is composed entirely of cartilage. In most elasmobranchs the cartilage is in 

 many places hardened by deposits of calcareous material without, however, assuming the 

 histological character of true bone. In Chlamydoselachus, it appears that such calcifi' 

 cation is very limited in extent. Thus Garman (1885.2) writes that the cartilage of the 

 skull is soft except in the parachordal region where it is hard and granular. Allis (1923) 

 says of the skull of Chlamydoselachus: ''The entire postero ventral region of the chon' 

 drocranium is extensively calcified in all my specimens, my observations thus differing 

 from Goodey's" (1910.1, p. 553). Goodey does mention (p. 543) a calcification of the 

 floor of the cranium in the region of its junction with the vertebral column, and elsewhere 

 in the same article he describes local calcifications forming the rudimentary centra of the 

 vertebrae, but he emphasizjes (p. 553) ''the small amount of calcification appearing in the 

 skeleton at all." 



In the softness of its cartilaginous endoskeleton, Chlamydoselachus agrees with 

 Heptanchus which, according to Daniel (1934), has cartilage of the clear hyaline variety 

 with very little in the nature of calcareous deposits. In both genera this is probably 

 a primitive character. 



THE SKULL OF CHLAMYDOSELACHUS 



The vertebrate skull consists of the cranium and the visceral skeleton. The cranium 

 serves to protect the brain and certain sense organs: the olfactory organs, the eyes and 

 the membranous labyrinths. The visceral skeleton consists of a series of cartilaginous or 

 bony arches which partly surround the mouth and the pharynx. These arches comprise 

 the jaws or the mandibular arch, the hyoid arch, and the branchial arches or gill'arches. 

 The term cranium is sometimes used as a synonym for skull. The cranium is then divisi' 

 ble into two portions, the cerebral cranium or neurocranium, and the visceral cranium 

 or branchiocranium. 



