2 20 Memoir Sears Foundation for Marine Research 



Generic Characters. Two dorsal fins, the origin of the ist considerably posterior to 

 origin of pelvicsj dermal denticles along dorsal margin of anterior part of caudal not 

 enlarged or modified as a distinct crest, or bounded below by a band of naked skin on either 

 side; nostrils entirely separate from mouth, their anterior margins without barbels and 

 falling considerably short of mouth j posterior as well as upper margin of nostril expanded 

 as a flap; labial furrow around corner of mouth and on each jaw; interspace between anal 

 and caudal less than Vs as long as base of anal; base of anal more than twice as long as base 

 of 2nd dorsal; no fold below eye; mucous pore system on lower surface of snout very con- 

 spicuous; gill openings either of the usual conformation, or so deeply concave anteriorly 

 that tips of gill filaments are exposed; 5th gill opening over or behind origin of pectoral; 

 teeth numerous, those in front of mouth with one chief cusp and one or more smaller cusps 

 on each side; several series of teeth functional. 



Range. Both sides of North Atlantic, including Iceland; South Africa; west coast of 

 North America from Gulf of California to Puget Sound; Hawaiian Islands; Japan; 

 Philippines and East Indies; Indian Ocean and Gulf of Aden; west coast of South Africa. 



Species. These are little known sharks of deep water, the majority of them so far 

 known from very few specimens. The named species of the genus, numbering 13 and 

 from widely separated seas, resemble one another very closely in general appearance, but 

 they appear to be separable by sufficiently precise differences. Fowler has even distributed 

 them among three subgenera,^ according to the degree of cirrus-like development on the 

 margins of the nostrils, anterior and posterior. According to published accounts, however, 

 and to our own study of three of the species, the differences in this respect are not sharp 

 enough to serve as a basis for generic separation. Nevertheless, the members of the genus 

 do fall into two sharply contrasting categories as regards the gill openings, for while 

 these are of the ordinary type in one group, typified by A. brunneus Gilbert from the 

 west coast of North America, they are close together above and below in other species, 

 but so deeply concave anteriorly at the midlevel that the tips of the gill filaments are 

 exposed (p. 227). It is astonishing that attention has not been directed to this earlier, 

 for the gills are clearly pictured thus mA. atlanticus Koefoed," as well as in ^ . microps Gil- 

 christ.' Furthermore, a re-examination of the specimens in the United States National 

 Museum shows gills of this same type in profundorum Goode and Bean, 1895 (p. 222), 

 verweyi Fowler, herklotsi Fowler, 1934,* spongiceps Gilbert, 1905, and platyrhynchus 

 Tanaka, 1909,° although no suggestion of the fact appears in the published accounts 

 or in the illustrations of these species. Under ordinary circumstances a diflterence so 

 striking would demand the institution of a new genus. In the present case, however, such 

 action does not seem advisable because neither the account nor the illustration of the type 



1. Bull. U.S. nat. Mus., loo (15), 1941: 53; Parapristurus, Pentanchus and Afristurus. 



2. Koefoed, Rep. Sars N. Atlantic Deep Sea Exped., 4 (i), 1932: 18, pi. 3. 



3. Mar. biol. Rep. Cape Town, 2, 1922; 46, pi. 7, fig. i. 

 4.. Proc. Acad. nat. Sci. Philad., ^5, 1934: 237, 238. 



5. There is a specimen of this species in the United States National Museum, although not the type. 



