14 THE PLAGIOSTOMIA. 



No pits at the root of the caudal. Margin of first gill cover free across the isth- 

 mus. Intestine with a spiral valve. Pterygoquadrate not articulated to 

 postorbital process of the skull, hyomandibular elongate. 



Chlamydoselachus. 



Chlamydoselachus Garman, 1884, Bull. Essex inst., 16, p. 52. 



Six gill openings, margin of first free across the isthmus. Mouth very wide, 

 longer than the skull, without labial folds. Teeth raptorial, similar in the two 

 jaws, each with a broad base and three slender, curved, subconical cusps, with 

 or without rudimentary cusps at their bases; no median teeth in the upper 

 series; a median series on the symphysis below. Eyes lateral, elongate. Fins 

 broad, caudal without a notch. C. lawleyi Davis occurs in the Pliocene of 

 Tuscany. 



Chlamydoselachus anguineus. 



Plate 59, fig. 4-5 (egg, embr.), fig. 6 (br. skel.); Plate 61, fig. 7-8 (embr.). 



Chlamydoselachus anguineus Garman, 1884, Jan. 17, Bull. Essex inst., 16, p. 47, fig. 5, 1884, Feb. 1, 

 Science, 3, p. 116; 1884, Mar. 21, ibid., p. 345; 1884, Nov. 28, ibid., 4, p. 484; 1885, July, Bull. 

 M. C. Z., 12, p. 1, pi. 1-20; 1885, Proc. Amer. assoc. adv. sci., 20, p. 536; 1887, Mar. 18, Science, 

 9, p. 267; 1888, Bull. M. C. Z., 17, p. 82, pi. 15; 1899, Mem. M. C. Z., 24, p. 41-44, pi. 70. 



Didymodus anguineus Cope, 1884, Mar. 7, Science, 3, p. 275; 1884, April, Amer. nat., 18, p. 413; 

 1884, Proc. Amer. philos. soc, 21, p. 412; 1884, May 30, Science, 3, p. 645 (changes of name); 

 1884, Proc. Amer. philos. soc, 21, p. 572. 



Chlamydoselache anguinea Gunther, 1887, Challenger rept. Zool., 22, p. 2, pi. 64, 65; Dean, 1895, 

 Fishes, living and fossil. 



Body long, slender, subcylindrical, compressed behind the vent, which is 

 behind the middle of the total length. Head broad, wider than high, slightly 

 convex. Snout broadly rounded, hardly extending beyond the jaws. Nostrils 

 lateral, behind the forward end of the mouth. Eye rather large, elongate, about 

 midway from eye to end of snout, near a vertical from the mid length of the 

 mouth. Spiracle very small, distance behind the eye about equal to distance 

 from eye to end of snout. Mouth very large, extending as far backward as the 

 skull; upper and lower jaws of equal length. No labial folds. Teeth small, 

 similar in both jaws, several of each row in function; each tooth with three long, 

 slender, curved, backward directed cusps. A small cusp at the base of the 

 middle cusp is not always present. Bases of teeth broad, each with two prongs 

 reaching backward beneath the base of the next tooth in the row. Upper jaw 

 with fourteen rows on each side, no median row. A median row on the symphysis 

 of the lower jaws with thirteen rows on each side of it. Pterygoquadrate at- 

 tached to the skull in front of the postorbital process, between the eyes. Gill 



