POLYCLADS OF THE ATLANTIC COAST — HYMAN 477 



HOPLOPLANA INQUILINA THAISANA Pearse, 1938, new combination 

 Hoploplcna thaisana Peaese, 1938, p. 79, fig. 28. 



Material. — One whole mount, labeled Hoploplana thaisaiia, type, 

 U. S. N. M. No. 20189. 



Form. — Oval, flat, 1 to 3 mm. long, 0.7 to 2.1 mm. broad; with 

 conical tentacle.^. 



Eyes. — Eyes, 10-26 around and in each tentacle base; 2-11 eyes in 

 each cerebral group. Pearse claims the tentacular group is rounded 

 in H. thxiisana and horseshoe-shaped in H. inquilina. Wheeler's fig- 

 ure fails to show any difference from Pearse's of H. thaisana (Pearse, 

 1938, fig. 28) in this regard. In the two whole mounts of H. inquilina 

 available to me at the present writing, the tentacular eyes do show 

 a somewhat semicircular grouping but whether this arrangement 

 is constant can be determined only by examination of large numbers 

 of both forms. 



Color. — Not stated by Pearse. 



Digestive tract. — As in H. inquilina; claim of Pearse that the bases 

 of the pharynx folds are less lobulated in thaisana than in inquilina 

 could not be substantiated by comparison of the available specimens. 



Reproductive system. — Only briefly mentioned by Pearse ; what he 

 calls the seminal vesicle is the prostate. As there was but the one 

 specimen of thaisana. in the collection I have forborne to section it. 

 Attempts to obtain additional material proved futile. As far as I 

 can determine from examination of the stained type specimen, the 

 copulatory complex is identical with that of H. inquilina. 



DiMrihution. — St. Vincent Bar, Apalachicola Baj-, Fla. 



Habits. — Commensal in the snail Thais ■floridana -floridana; also 

 found with oysters and barnacles. 



Remarks. — In so far as can be determined from the available data 

 and material, H. thaisana differs from H. inquilina only in its smaller 

 size and in its commensalism with a different snail host. I am 

 therefore of the opinion that it is at best a geographical subspecies 

 and hence sliould be named H. inqiiilina thaisana. 



Family PLANOCERIDAE Lang, 1884 (emend. Bock, 1913) 



Definition. — Schematommata with a cirrus; cirrus sac lined by 

 spines, hooks, or ridges eversible to the exterior, or a long cuticuiar- 

 ized papilla may be present; often with tentacles; true or accessory 

 seminal vesicles; prostate free or interpolated; vagina often highly 

 muscular; uteri not confluent anterior to the pliarynx. 



