94- Memoir Sears Foundation for Marine Research 



not beak-like, without lateral teeth or cirri; teeth alike in both jaws, those in front of 

 mouth essentially similar to those toward corners; trunk subcylindrical (shark-like) ; eyes 

 lateral; anterior margins of pectorals not expanded forward beyond ist gill opening; 

 mouth terminal, without distinct snout; nostril entirely separate from mouth, its anterior 

 margin without barbel; eye without nictitating membrane; spiracles present; vertebral 

 column only incompletely segmented, the notochord being somewhat constricted segmen- 

 tally for a short distance back from head, but of uniform diameter thence rearward; a few 

 of anterior vertebrae with primary calcifications (cyclospondylic), but the others not cal- 

 cified; upper jaw (palatoquadrate cartilage) with transverse process attached to orbital 

 region of cranium by a ligament (only attachment to cranium) ; also with ligamentary 

 attachment to the hyomandibular arch, which is well developed and provides the chief 

 suspension for both jaws; propterygial cartilage of pectoral fin bears no radial elements; 

 heart valves in 6 or 7 rows ; clasper of male not enclosed by margin of pelvic fin, its axial 

 cartilage attached to basipterygial cartilage of fin by i small element only, its tip with 3 

 movable accessory cartilages. Development ovoviviparous.^ 



Remarks. The majority of recent authors have placed Chlamydoselachus (sole 

 known representative of the group) among the notidanoids because of its large number of 

 gill openings and the incomplete segmentation of its vertebral column. We believe a sepa- 

 rate suborder is demanded for it," because it differs so widely from Hexanchus and 

 Heptranchias (representing the notidanoids) in the much less intimate attachment of its 

 upper jaw to the cranium, as well as in the facts that its much larger hyomandibular arch 

 affords the chief suspension for the jaws and that its notochord is of nearly uniform diame- 

 ter throughout most of its length. 



Families, Genera, Species. Only one modern species is known, Chlamydoselachus 

 anguineus Garman; but teeth, apparently of this genus, have been described from the 

 Pliocene of Tuscany. 



Range. Japan, also eastern Atlantic off southern France, off the Iberian Peninsula, 

 and near Madeira in moderately deep water; reported from New South Wales, but on 

 doubtful evidence.' 



Fossil Teeth. From Miocene, West Indies; Pliocene, Europe. 



1. See Garman (Bull. Mus. comp. Zool. Harv., :2 [i], 1885), Goodey (Proc. zool. Soc. Lond., 1910: 540), Allis 

 (Acta zool., 4, 1923: 122) and Smith (Dean Memor. Vol., Amer. Mus. nat. Hist., Art. 6, 1937) for detailed 

 accounts and illustrations of the skeleton and other anatomical features; Garman (Mem. Harv. Mus. comp. 

 Zool., 36, 1913; pi. 59, fig. 4, 5, pi. 61, fig. 7, 8) and especially Gudger (Dean Memor. Vol., Am. Mus. nat. 

 Hist., Art. 7, 1940) for excellent illustrations of the egg capsule and of embryos in different stages of develop- 

 ment. 



2. Garman (Science, 5, 1884: 1 17) proposed for Chlamydoselachus a new order, Selachophichthyoidi, a name based 

 on the supposition that it "stands nearer the true fishes than do the sharks proper." Shortly afterward, however. 

 Gill (Science, 3, 1884: 346) united it with the fossil genus Didymodus (a pleuracanth) as the suborder Pterno- 

 donta, while Garman (Bull. Mus. comp. Zool. Harv., ii, 1885: 30) united it, as Cladodonti, with the fossil 

 Cladodui and its allies, of which he, by then, had come to consider it "the living representative." More recent 

 studies of the fossil genera in question, however, make it so unlikely that Chlamydoselachus can be properly 

 grouped with any pleuracanth or cladodont that we prefer to use for the suborder a name based on that of the 

 modern genus. 



3. See Whitley (Fish. Aust., r, i94i: 70). 



