180 DEACHMANN 



(In one of the individuals was discovered an ovigerous female of an 

 oyster crab. According to Dr. Fenner A. Chace, U. S. National Museum, 

 it is a new species and seems to be related to Pinnotheres hirtimanus 

 H. Milne Edwards, from the waters around Cuba.) 



Athyone glasselli (Deichmann) 



Thyone glasselli Deichmann, 1936, p. 65, text figures; 1937, p. 171, 



fig. 2. 

 Athyone glasselli Deichmann, 1941, p. 119. 



Diagnosis: Large species which superficially resembles the Atlantic form, 

 Thyone briareus (Lesueur), with numerous feet and 10 tentacles of 

 which the two ventral ones are small. Skin leathery with few spicules, 

 color brownish to blackish, mottled, with dark introvert and tentacles. 

 Calcareous ring stout, short-tubular, with well developed tails on the 

 radials, and tall interradials which posteriorly are excavated. One dor- 

 sally attached stone canal and two ventrally placed Polian vesicles. 

 Gonads as two tufts of tubes placed near the middle of the body. Longi- 

 tudinal muscles strong, fleshy, in contracted specimens projecting like 

 ridges. 



Spicules as small tables, with oval to squarish disk with 4 to 8 holes 

 and two pillars ending in many spines, with age reduced to oval or 

 round plates. Feet with well developed end plate, surrounded by elon- 

 gate, perforated plates; in the wall two-pillared, elongate supporting 

 tables which in older individuals become reduced to spectacle or lozenge- 

 shaped plates or rods. Introvert with delicate tables with numerous holes 

 in the disk and low, two-pillared spire; rosettes present, as also in the 

 tentacles. 



Type specimen: In the Museum of Comparative Zoology. 

 Type locality: Punta Penasco, Sonora, Mexico. 

 Distribution: Known from the type locality and Guaymas, Sonora, 



Mexico. 

 Depth: Found in shallow water, covered by sand. 

 Specimens examined: The type and the two "headless" individuals, about 



7 cm in diameter, strongly contracted, from Guaymas. 

 Remarks: As noted in the original description, the species resembles super- 

 ficially Thyone briareus (Lesueur) from the Gulf of Mexico, Florida, 

 and the Atlantic Seaboard northwards to Woods Hole, Massachusetts. 

 However, in fully expanded condition the species must be somewhat 

 larger than briareus and it appears also to be a more robust form in 



