GULF OF MEXICO 



399 



2 Thyonella sabanillensis (Deichmann) 



Thijone sabanillensis Deichmann, 1930, p. 178, pi. 17, 

 figs. 4-19. 



Thyonacta sabanillensis Deichmann, 1941, p. lOI. 



Diagnosis. — Large form, 15 cm. Resembles a 

 somewhat more delicate T. (jemmata, with stronger 

 tendency to papillae toward the ends of the body 

 and dorsally. Color uniformly grayish brown. 

 Spicules an external layer of flattened baskets with 

 uneven margin with blunt teeth and four small 

 accessor}' holes besides the four central ones. 

 Inner layer buttons with strongly knobbed surface 

 and irregular plates with undulating to smooth 

 surface. Feet without end plate, walls with 

 curved thick supporting rods with small holes. 

 In papillae often triangular plates, more or less 

 strongly bent. Introvert with rosettes; tentacles 

 with perforated rods which decrease in size toward 

 the tips. Type: United States National Museum. 

 Type locality : Sabanilla, Columbia, shallow water. 

 Distribution: So far known only from the type 

 locality and the western part of the Gulf of 

 Mexico, coast of Texas (Hedgpeth). Few fathoms 

 depth. 



3 Thyonella pervicax (Th6el) 



FIG. 67: 12-20 



Thyone pervicax TMe\, 1886a, p. 93, pi. 5, fig. 9; pi. 2, 

 fig. 3; Deichmann, 1930, p. 175, pi. 16, figs. 9-12. 



Diagnosis. — Medium sized form, 7 cm. long, 

 with rigid skin; ventral tentacles small; tube feet 

 with conical base, covering the surface completely 

 even in small individuals, at utmost with a faint 

 indication of serial arrangement along the ambu- 

 lacra. Color white or pale brown, sometimes with 

 brown spots. Spicules an external layer of 

 flattened cups with large marginal spines; an inner 

 layer of four-holed, strongly knobbed buttons of 

 two sizes. Feet with small end plate or none and 

 walls stiffened by slightly curved rods, spectacle- 

 shaped with one or more holes in each end. Type: 

 British Museum. Type locahty: Bahia, Brazil. 

 Distribution: Reported from the type locality, 

 Tortugas, and other localities on the Gulf side of 

 Florida. Occasionally dredged in Vineyard Sound. 

 Seems always to be taken 'at some fathoms depth. 

 Although the species has spicules somewhat similar 

 to gemmata they are nevertheless sufficiently 

 different to prevent misidentification. Aside from 

 the differeiices in the calcareous ring pervicax has 

 more feet even at an early stage than has gemmata 



and the latter is also more darkly colored. It is 

 evidently one of the most common species off the 

 west coast of Florida. 



Genus 6 EUTHYONACTA nom. nov. 



New name for Thyone solida (Deichmann). 



Eiithyonacta solida Deichmann 



Thyone solida Deichmann, 1930, p. 172, pi. 15, figs. 

 11-17, pi. 16, figs. 1-2. 



Diagnosis. — Heavily built, thick-skinned form 

 with barrel-shaped body, five heavy oral valves 

 and tube feet scattered uniformly over the body, 

 more papilliform on the dorsum and at the ends. 

 Color in alcohol yellowish brown. Simple ring. 

 Spicules an outer layer of deep baskets with a 

 wreath of teeth along the rim and an inner layer 

 of regularly knobbed buttons of varying size. 

 Feet apparently without end plate, though a num- 

 ber of branched rods may substitute for such one; 

 walls packed with heavy rods, often with a third 

 arm. Introvert with rosettes and small buttons 

 with almost smooth surface. Tentacles with 

 strong, perforated rods, decreasing in size toward 

 the tips. Type: United States National Museum. 

 Type locality: Gulf of Mexico, Albatross station 

 2369. Distribution: So far known only from the 

 Gulf of Mexico from 26 to 30 fathoms depth. 

 The largest individuals examined were about 6 

 cm. long with the tentacles retracted. From the 

 size of the gonads I judge that the species may 

 reach a much larger size, 15 to 20 cm. or there- 

 about. It was taken from coarse gray sand and 

 broken corals in which it most likely lives con- 

 cealed. 



Genus 7 PENTACTA Goldfuss 1820 

 Pentacta pysmaea (Theel) 



FIG. 67; 4-11 



Coluchirus pygmaeus Theel, 1886, p. 92, pi. 4, fig. 9. 



Pentacta pygmaea, Deichmann, 1930, p. 180, pi. 21, figs. 

 10-16. 



Diagnosis. — Medium-sized form, 7 cm. long, 

 with short, box-like body, with cylindrical feet in 

 three bands on the ventrum; dorsal side with 

 blunt papillae along the ambulacra with some 

 tendency to spread out into the interambulacra. 

 Strong oral valves with papillae. Color chocolate 

 brown, paler below. Spicules an external layer of 

 deep baskets often with rim incomplete; an inner 

 layer of strongly knobbed four-holed buttons 

 with 10 knobs besides a varying number of much 



