FREE-LIVING FLATWORMS (TURBELLARIA) OF THE GULF OF MEXICO 



By L. H. Hyman, American Museum of Natural History, New York City 



Very little information is available concerning 

 the free-living flatworms of the Gulf of Mexico. 

 Nothing at all has been done with the smaller 

 and microscopic forms so that available material 

 is limited to the polyclads (order Polycladida), 

 and these have been studied only for the Gulf 

 coast of the United States. To the writer's 

 knowledge, no study has ever been made of the 

 turbellarian fauna of the Mexican coast of the 

 Gulf. 



The most extensive work on the littoral poly- 

 clads of the Gulf of Mexico was done by Pearse 

 (1938) during a stay in the region of Apalachicola 

 Bay near the Alabama border of Florida. This 

 publicatioa, unfortunately, contains some errors. 

 The writer revised Pearse's work in 1940, and the 

 names considered valid are those employed in 

 that article. 



The most common littoral polyclads of the Gulf 

 coast, distributed from Florida to Texas, are Sty- 

 lochiLs frontalis Verrill {=Sty. inimicus Palombi, 

 1931), Stylochus ellipticus (Girard) 1850 {^Eusty- 

 lochus meridionalis Pearse, 19S8) , Hoploplana in- 

 quilina (Wheeler) 1894, and Gnesioeeros floridana 

 (Pearse) 1938 {=Stylochoplana floridana Pearse, 

 1938) . Illustrations and descriptions of these spe- 

 cies will be found in Pearse (1938) and Hyman 

 (1939a, 1940). Stylochus frontalis is an oval, gray 

 worm up to 50 mm. in length with nuchal tentacles 

 and a band of eyes around the entire body margin. 

 It lives in association with oysters on which it 

 feeds and to which it may become quite destructive, 

 hence being of some economic importance. The 

 ecology of this polyclad has been treated at some 

 length by Pearse and Wharton (1938). Stylochus 

 ellipticus is an oval, gray, olive, cream, or brownish 

 worm with nuchal tentacles and with marginal 

 band of eyes extending only along the anterior 

 part of the body. It, also, is often associated 

 with oysters but is a general littoral species. 

 Hoploplana inquilina is a small, oval, rather 

 transparent worm that inhabits the mantle cavity 



of Busycon and Thais, possibly other gastropods. 

 Pearse (1938) attempted to separate the form 

 living in Thais from that in Busycon as a distinct 

 species thaisana, but the writer failed to find any 

 good grounds for this distinction and considers 

 thaisana to be, at best, a geographical variant. 

 Schechter (1943) found H. inquilina living in 

 Thais floridana at Barataria Bay, La. Gnesioeeros 

 floridana, a small, somewhat transparent worm of 

 cuneate form, with nuchal tentacles but without 

 any marginal eyes, is of common occurrence along 

 the Gulf coast. A number of specimens of this 

 species were sent to the writer by Joel W. Hedg- 

 peth who collected them at Port Aransas, Tex., 

 and many were recorded by Pearse from the west 

 coast of Florida. In an Annotated List of the 

 Fauna of the Grand Isle Region 1928-1941, pub- 

 lished by the marine laboratory of Grand Isle, La., 

 there is mentioned Gnesioeeros sargassicola lata; 

 this is presumably a misidentification of Gnesio- 

 eeros floridana. 



Other polyclads described by Pearse from the 

 Apalachicola Bay, Fla., region are: Coronadena 

 mutabilis (Verrill) 1873 { = Discocelis grisea Fe&rse, 

 1938); Latocestus whartoni (Pearse) 1938 ( = Oculo- 

 plana whartoni Pearse, 1938); Stylochus oeuliferus 

 (Girard) 1853 (=^Stylochu^ floridanus Pearse, 

 1938); Zygantroplana angusta (Verrill) 1893 

 {=Stylochoplana angusta (Verrill) Hyman, 1939); 

 Euplana gracilis (Girard) 1850 {^Conjuguterus 

 parvus Pearse, 1938); Enantia pellucida (Pearse) 

 1938 {^Acerotisa pellucida Pearse, 1938); a 

 species of Thysanozoon possibly brocchi (Risso) 

 1818; Pseudoceros maculosus Pearse, 1938; Oli- 

 goclado floridanus Pearse, 1938 { = Hymania pry- 

 therchi Pearse and Littler, 1938); and Prosthiosto- 

 mum lohatum Pearse, 1938. None of these species 

 have been found in other parts of the Gulf of 

 Mexico except Florida, but some of them extend 

 up the Atlantic coast to the Carolinas. Descrip- 

 tions and figures of these species are given in the 

 articles by Pearse (1938), Pearse and Littler 



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