POLYCLADS OF THE ATLANTIC COAST HYMAN 461 



mens having a typical eye arrangement. I therefore refer all Pearse's 

 specimens to S. ellipticas. A whole mount, U. S. F. C. No. 14398, 

 collected under ti wharf at Woods Hole, Mass., September 19, 1882, 

 and labeled by Verrill Planocera nebulosa is Stylockus ellipticus. 



STYLOCHUS FRONTALIS Verrill, 1892 



Stylochus frontalis Vejirill, 1892, p. 465, pi. 44, fig. 1. 



Stylochus inimicus Palombi, 1931, p. 218, figs. 1-4; pi. 4, figs. 1-4 — Peaese, 1938, 



p. 69, fig. 23.— Pe.\rse aud Whabton, 1938, figs. 1-21. 

 Stylochus tenax Palombi, 1936, p. 4, figs. 1-7 ; pi. 1, figs. 1, 2. 



Matenal. — Many whole mounts collected by Pearse. 



Form. — Oval, flat, of firm consistency, up to 50 mm. long by 27 mm. 

 wide; tentacles conical, slightly tapering, very retractile (Pearse, 

 1938, fig. 23). 



Eyes. — Numerous eyes in, some around, tentacles; cerebro frontal 

 eyes begin behind tentacles as paired elongate groups coming to a 

 point posteriorly; anterior to tentacles these merge and spread in fan 

 shape to join marginal band. Marginal band completely encircles 

 margin, but is wider and of larger eyes anteriorly, diminishing 

 posteriorly. 



Color. — Gray or yellowish gray, lighter toward margins; Verrill 

 reports some mottling with brown in a single specimen he had ; Pearse 

 and Wharton indicate a median light line. 



Digestive tract. — Pharynx central, large, elongate, richly ruffled, 

 with about five or six main branches on each side; mouth central; 

 intestine richly branched, not anastomosed. 



Repi'oductive system-. — Figured and described by Palombi, 1931, 

 1936. 



Dii'trihiotion. — Florida to Texas, oyster beds; probably also north- 

 ward to the Carolinas. 



Habits. — Found among living and dead oyster shells; feeds chiefly 

 on oysters ; biology described by Pearse and Wharton, 1938. 



Remarks. — Verrill found a single specimen, 25 by 12 mm., on the 

 bottom of a ship that had come from the Carolina coast (see further 

 under StyJochoplana angusta). There are only two stylochids com- 

 mon in that region — S. ellipticus and >S'. inimicios. Verrill's figure of 

 the eyes clearly indicates S. inimicus, and his description also agrees 

 satisfactorily with this species. I am therefore of the opinion that 

 S. inimicus and S. frontalis are identical. Palombi assigned Florida 

 stylochids preying on oysters to two species, S. inimicus and S. tetiax. 

 Pearse is of the opinion that these are conspecific. The IT. S. National 

 Museum has lent Palombi's paratypes of >S'. tenaa; for examination, and 

 I have sectioned the copulatory apparatus of one of them. The para- 

 types are certainly very much thicker than any specimens of >S'. 



