NO. 3 DEICHMANN: HOLOTHURIOIDEA ; PART I, DEXDROCHIROTA 131 



Remarks. — The species seems to be the most characteristic holothurian 

 from the coasts of Peru and certain localities in Chile. In some cases it 

 occurs in the same localities as Athyoniditim chilensis, but the 2 species 

 have an entirelj^ different ecology. Pattalus mollis is found completely 

 exposed, clinging to rocks, while Athyonidium chilensis is found buried 

 in sand with its tentacles extending flatly on the surface (H. L. Clark, 

 observed on the Hancock Expeditions in the spring of 1938). In pre- 

 served condition the 2 species are entirely unlike except in size; P. mollis 

 is uniformly purplish red or faded brown, while the other species is mot- 

 tled gray, sometimes with almost black dorsum, black tentacles, and more 

 lightly colored ventrum. Internally P. mollis has large well-developed 

 interradials with long anterior tooth, while Athyonidium chilensis has 

 broad radials and the interradials are almost completely resorbed or hid- 

 den in the leathery tissue. 



It would be tempting to select Lesson's name peruanus for this species 

 so typical of Peru, especially since material in the M.C.Z. shows that 

 Pattalus mollis does occur in Payta, Peru, the type locality for Lesson's 

 species. But there is still the possibility that Lesson did have a true deka- 

 chirote form before him, with 2 smaller ventral tentacles which were 

 overlooked, a form which has not as yet been rediscovered except possibly 

 by Troschel. Furthermore, both P. mollis and A. chilensis often occur in 

 the same localities, and Lesson's description and figures may refer to a 

 composite species, the low number of tentacles — although incorrect — 

 being taken from A. chilensis, while the color note "rouge violet eclatant 

 et fonce" refers to P. mollis. 



No other species has caused so much confusion in the literature as this 

 species (including A. chilensis). It has usually been identified with Les- 

 son's Holothuria peruana, although, if Troschel is correct, the latter is 

 one of the members of the genus Thyone s.l. 



Semper obviously referred some of his material of A. chilensis — those 

 in which he observed the 10 inner small tentacles — to this species and 

 commented on the variability of the number and size of the tentacles in 

 this genus; Lampert did the same, as also H. L. Clark. 



Verrill referred his material of mollis to Anaperus peruanus Troschel 

 but realized the discrepancy in the number of tentacles and corrected the 

 name to "Pattalus peruanus — closely related to Selenka's P. mollis," 

 without indicating wherein the 2 species differed. 



The reasons why P. mollis cannot represent the mature stage of 

 Euthyonidium ovulum Selenka are mentioned above (under that species). 



