GULF OF MEXICO 



397 



Texas to Florida and nortlnvard along the At- 

 lantic seaboard to Woods Hole, Mass. Shore to 

 few fathoms depth, in muddy localities, often at- 

 tached to eelgrass in muddy sheltered localities. 

 At Cocoplum Beach in Bisca>nie Bay, H. L. Clark 

 dug it out of the mud in the same localities as 

 Leptosynapta micropafina while in Woods Hole the 

 year-old individuals were picked off the eelgrass. 



The species has been extensively used for ex- 

 perimental work at Woods Hole and may possibly 

 be even more useful in the South where many 

 animals are more tolerant to warm water than 

 they are in the Nortti. 



In Woods Hole, T. briareus breeds in June- 

 July but very likely the season is earlier in the 

 Gulf and around Florida. The eggs are small 

 and develop in S% days (Ohshima 1925) into a 

 creeping larva which soon acquires tentacles and 

 after 3 months is completely equipped with 

 spicules of the same type as in the adult though 

 naturally scaled down to the size of the few milli- 

 meter long specimens. In June, the following 

 year, the smallest individuals found measure 2 cm. 

 in length with no trace of genital organs. In 

 specimens 3 to 4 cm. long gonads are present and 

 increase the following years in length and number 

 of the tubes. After 5 years the animals are ready 

 to spawn, but whether they die after the spawning 

 or regenerate the gonads is not known. The 

 spawning has been studied by Colwin (1948). 



Kille has studied the regeneration of the ten- 

 tacles which is accomplished in 3 weeks. Extir- 

 pated gonads regenerate very fast if small pockets of 

 germ cells are left; if completely removed it will take 

 several months before the glands stage a comeback. 



It is one of the few species which as far as knowa 

 has no parallel form in the Panamic region. 

 Troschel had apparently some mislabeled Thyone 

 briareus which he described as Anaperus peruviana 

 (Lesson), a deep purple form with simple cal- 

 careous ring. As the Panamic region recently 

 has been rather thoroughly explored by the Han- 

 cock Expeditions it seems rather unlikely that so 

 large a species as one resembling T. briareus could 

 have escaped attention. 



Thyone inermis Heller 



Thyone inermis Heller, 1868, p. 78; Deichmann, 1947, 

 p. 84, pi. 1, figs. 7-13; pi. 2, figs. 1-17. 



From Tobago, British West Indies, and Florida 

 has occasionally been reported a small species 



which, with some doubt, has been referred to 

 T. fusus (O. F. Miiller), the well-known type 

 species from the northeastern Atlantic. It ap- 

 pears, however, that one has been dealing with a 

 southern species typical of the Mediterranean 

 and the waters around Portugal, the Azores, as 

 far north as Roscoff, France. 



As the American material always has been 

 immature, few centimeters long, it seems likely 

 that the species appears intermittently only and 

 has been unable to be established in the western 

 Atlantic. It is included here because a somewhat 

 similar form is known from the Panamic region, 

 and if it has a parallel form in the Caribbean and 

 the Gulf one might be inclined to identify it with 

 the European invader which most likely does not 

 extend its range into the Gulf. 



Genus 3 NEOTHYONE Deichmann 



Neoihyone Deichmann, 1941, p. 106; new name for 

 Selenka's Stolus gibber, 1867, p. 356 and allied forms. 



Remarks. — In the Panamic region three species 

 have been referred to this genus. In the West 

 Indian region only one species is known, previ- 

 ously listed under three different names. 



Neothyone belli (Ludwig) 



FIG. 67: 21-22 



Thyone belli Ludwig, 1887, p. 21, pi. 1, figs. 10-13; 

 Deichmann, 1930, p. 176, pi. 14, figs. 10-13. 



Thyone micropiinctata Sluiter, 1910, p. 338, text fig. D 

 a-c; Deichmann, 1930, p. 171, pi. 14, figs. 14-18. 



Cucumaria argillacea Sluiter, 1910, p. 336, text fig. B a-c; 

 Deichmann, 1930, p. 160 (not examined). 



Diagnosis. — Small form, 5 cm. long, with skin 

 rigid from the numerous spicules. Color dirty 

 gray, sprinkled with dark spots. Spicules knobbed 

 buttons with six margmal knobs and two central, 

 often fused to a handle. Type: Wiirzburg; 

 Sluiter's type may be in Germany. Type locality: 

 Abrolhos Reefs, Bahia, Brazil; Sluiter's types 

 came from Tortugas, Florida. Distribution: From 

 Abrolhos Reef, Brazil, to Colon Harbor, Panama, 

 including Trinidad and Tobago. Also taken at 

 Tortugas. Shore to 12 fathoms. 



Reexamination of the available material of T. 

 belli and T. micropunctata has convinced me that 

 the two species cannot be kept separate, and 

 undoubtedly Sluiter's 8 mm. long C. argillacea, 

 taken at the same locality as his micropunctata is 

 the young of the latter. The differences in the 

 calcareous ring which his figures indicate are such 



