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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I42 



ternal pelvic structures have been neglected. The most thorough 

 account of pelvic anatomy in fishes is that of Sewertzoff (1934); 

 within groups, Sheldon's (1937) treatment of the pelvic girdle in cat- 

 fishes appears to be unique. The facets of pelvic structure that will 

 be treated here are the small, curved splint of bone that lies outside of 

 the outermost ray in many lower teleosts, and the radial elements. 



The pelvic fins of most lower teleosts are made up of a series of 

 segmented soft rays (lepidotrichia of Goodrich, 1904, Jarvik, 1959, 

 and others), each of which contains a separate upper and lower half. 

 The only exception is the curved splint that runs for most of its 

 length along the outer surface of the upper half of the outermost ray 

 on either side (fig. 5A to C). This splint never shows any transverse 



w 



A 



Fig. 5. — Outermost right pelvic ray bases, lateral views. 



A, Tarpon (Clupeiformes) ; B, Solivomer (Scopeliformes) ; C, Aphredodorus 

 (Percopsiformes) ; D, Myripristis (Beryciformes). 



segmentation, and its anterior end does not articulate with the pelvic 

 girdle but lies free in the skin. The origin and nature of this structure 

 seem to be unknown. Suffice it to say here that it can be traced back 

 in typical form and condition to Amia. In Lepisosteus there is a 

 minute, unpaired, diamond-shaped plate on the outside of the base 

 of the lateralmost ray, but whether this is the same element as the 

 curved strut of Amia seems open to question. 



Among the Clupeiformes this curved splint is present in Tarpon 

 (fig. 5A), Pterothrissus, Salmo, and Chanos among the forms ex- 

 amined. In the Dussumieriidae, Clupeidae, and Engraulidae it ap- 

 pears to be missing, at least as a separate element. 



There is probably no great systematic significance to be attached to 

 the loss of this splint. Thus, among the haplomous fishes it is present 

 in Esox but apparently not in Umbra. Among the iniomous fishes it 

 occurs in Solivomer (fig. 5B) but not in Aulopus. Among ostario- 

 physine fishes it appears in Brycon, and among the cyprinodonts, in a 

 specimen of Fundulus majalis (but not in another form of Fimdulus 

 examined). About all that can be said is that, like the orbitosphenoid, 



