NO. 3 DEICHMANN: HOLOTHURIOIDEA; PARTI, DENDROCHIROTA 125 



Thy one ovuluin Deichmann, 1936, p. 64 (passim). 

 Euthyonidiiim ovulum Deichmann, 1938, p. 380, text figure 12. 



Diagnosis. — Medium-sized form (probably about 10 cm. long) with 

 soft, thick skin with numerous soft feet. Tentacles 10 large external ones 

 and 10 inner ones which are much smaller and may be completely re- 

 tracted into small pockets. Calcareous ring with radials posteriorly broad 

 and deeply incised and tapering toward the anterior end; interradials 

 unusually broad and heart shaped with a slight posterior incision, ante- 

 riorly tapering to a point. Stone canals numerous and free, also several 

 Polian vesicles. Inner anatomy otherwise normal. 



Spicules a scattered layer of tables with irregular disk varying from 

 cross-shaped to a more or less branching or laciniated plate. Spire almost 

 always reduced to a few spines. Feet with large end plate ; supporting rods 

 are apparently totally lacking. Introvert seems to lack spicules; tentacles 

 with few rosettes and delicate rods. Spicules more or less completely re- 

 duced with advancing age and, except for the end plate, likely to be com- 

 pletely overlooked. 



Type.— M.C.Z. 



Type locality. — Acapulco, Mexico. 



Distribution. — From Lower California to Peru. 



Specimens examined. — Selenka's type specimens (3) and several spec- 

 imens from the Allan Hancock Expeditions : 



261-34. Tangola Tangola, Mex., 1 fm., March 1, 1934, 1 specimen. 

 591-36. Port Escondido, L. Calif., Mex., shore, March 16. 1936, 40 



specimens. 

 844-38. Lobos de Afuera Island, Peru, shore, February 14, 1938, 1 

 specimen. 



Remarks. — Re-examination of Selenka's type material of Stolus ovu- 

 lum showed that Selenka had overlooked the inner circle of tentacles 

 which were completely withdrawn into little pockets and that it was 

 identical with various individuals collected by the Hancock Expeditions, 

 and also by the Zaca. 



Euthyonidium ovulum has the same reddish-brown color which is 

 extracted in alcohol as the much larger species Pattalus mollis Selenka 

 from Peru and Chile. It would therefore be correct to consider whether 

 the two forms are merely growth stages of the form which possibly ought 

 to be called Pattalus peruana (Lesson) — see discussion under Pattalus 

 and Anaperus. Deichmann (1936) considered ovulum as possibly being 

 identical with Lesson's species (which was figured as having 8 tentacles) 



