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PROCEEDINGS OF THE NATIONAL MUSEUM 



sions as do show growth changes in R. porosus indicate a course of 

 development similar to that found in R. terraenovae. 



Only one mature male, 644 mm., was seen; the largest immature 

 male was 575 mm. The following tabulation presents the available 

 data on proportionate clasper lengths : 



The smallest non-embryo seen was 310 mm. The largest 

 embryo was 390 mm. The largest specimen examined was a stuffed 

 female from Brazil, approximately 1050 mm. 



Little data on sibling variation is available. Three embryos, 

 presumably siblings, from Saba Bank had 72, 73, and 74 precaudal 

 vertebrae. Two others from Cuba had 75 and 76 precaudal vertebrae. 



Distribution. — Essentially from the continental and insular shore- 

 lines of the western Atlantic between 24° N. and 35° S. latitudes. 

 Backus (1957) reported taking a specimen (as Scoliodon terraenovae) 

 from the surface about 65 miles north of Barbuda, where the depth 

 was about 3300 fathoms. 



Relationships. — See under Rhizoprionodon terraenovae (p. 604). 



NoMENCLATURAL DISCUSSION. — It is uot known whether a type 

 exists for S. porosus. The illustrations of the teeth and the description 

 are sufficient to establish that Poey had a species of Rhizoprionodon. 

 Since only one species of Rhizoprionodon occurs in Cuba, I have 

 elected to use Poey's name for it. 



Material. — Bahamas: Bimini, USNM 196526 (1: 775 mm.); about 

 three-fourths of a mile west of Riding Rock Light in 60 feet of water, 

 UMML 10410 (2: 797-844). cuba: USNM 9832 (2: ca. 248-ca. 251, 

 embryos), USNM 19795 (1: 710), USNM 33079 (1: 775); Havana, 

 CAS IU139 (1: 490), SU 10845 (1: 462), USNM 24793 (1: 758). 

 JAMAICA: USNM 9342 (2: 323-388), USNM 30014 (1: 501), USNM 

 30059 (1: 380), SU 11825 (1: 461), SU 11826 (1: 518), SU 11827 (1: 

 ca. 500), MNHN 1070 (1: ca. 430), NMV [no number] (1: ca. 385), 

 CNHM 2797 (1: ca. 409), CNHM 2799 (1: ca. 503). haiti: Port-au- 

 Prince Bay, ANSP 91757 (3: ca. 310-400), USNM 133660 (2: 525-ca. 

 535). SANTO DOMINGO [DOMINICAN REPUBLIC]: ANSP 77115 (1: 584), 



