The Embryology of Heterodontus jal^onicus 683 



scattered all over the body and fins. The authors list this species under the generic name 

 Gyropleurodus. 



To Kumada and Hiyama (1937) we are also indebted for figures representing dorsal 

 and lateral views of a young female H. francisci about 240 mm. (9.84 inches) long. In this 

 specimen, the supraorbital ridges are low in the middle third, as in the two specimens, 

 respectively young and adult, of H. quoyi examined by me. The color pattern of the 

 young specimen of H. francisci figured by Kumada differs from that of adults of this 

 species. The spots are larger and more complex; on the dorsal surface they are arranged 

 according to a definite pattern. The spots are more numerous on the dorsal surface than 

 on the lateral and ventral surfaces; on the fins, excepting the caudal, they are either in' 

 distinct or absent. Each spot consists of a very dark central portion surrounded by 

 a moderately dark zone. On the dorsal surface of head and body, the very dark spots 

 are grouped in about ten transverse rows, each imbedded in a moderately dark 

 stripe. On the body these stripes, each with its enclosed darker spots, are crescentic in 

 outline, the concave margin facing forward; but on the head there are, anteriorly, two 

 straight transverse stripes and, posteriorly, one crescentic stripe with its concave margin 

 facing caudad. Collectively, these transverse stripes form a pattern which is bilaterally 

 symmetrical with respect to the dorsal mid-line of the body. 



The skeleton of H. francisci has been described by Daniel (1914 and 1915). From 

 his figures it appears that the vertebral column is better developed and the notochord is 

 more constricted in Heterodontus than in Heptanchus (Daniel, 1934) and Chlamydoselachus 

 (Goodey, 1910, reviewed by Smith, 1937). 



My material for the study of H. francisci consists of two female specimens (one is 

 an adult) collected by Dr. 0. H. Townsend of the Albatross Expedition of the American 

 Museum of Natural History on April 10, 1911, at Angel de la Guardia Island, Gulf of 

 California. The larger specimen is about 705 mm. (27.75 inches) long, and the smaller 

 one 565 mm. (22.25 inches). Some additional measurements, for comparison with H. 

 quoyi, are given on page 684. 



The two specimens of H. francisci are much alike. In both, the head including the 

 gill'region is broad, but in the larger fish it is broader in proportion to the total length. 

 In the smaller and presumably younger specimen, the height of the head, in proportion to 

 its width, is greater. The larger shark has a decided hump between the head and the 

 first dorsal fin, but a similar hump on the smaller fish is less conspicuous. In both speci- 

 mens, the supraorbital ridges are rather tall. They are supported throughout their 

 length by the endoskeleton, and they terminate rather abruptly at their posterior ends. 

 The length of the first gill-sHt is about double that of the fifth, as in H. quoyi. The 

 spiracular openings are comparatively large: in the larger specimen their longer diameter 

 is from 4 mm. to 5 mm., in the smaller fish 3 mm. to 4 mm. Dorsal fins and dorsal spines 

 are larger than in H. quoyi. In both specimens, the origin of the first dorsal is directly 

 above the posterior margin of the pectoral base (as in Carman's H. japonicus). The hind 

 margins of both dorsals are concave. The base of the anal fin is slightly more than its 



