282 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 11 



Mostly shallow water forms living in the tropical region, either 

 freely exposed in the lagoon, or concealed among rocks, hidden in sand 

 or mud, or attached to rocks in the surf zone. A few species descending 

 to a depth of 200 to 250 fathoms and some extending into colder waters. 



Type genus: "Holothuria" Linnaeus 1758. 



Remarks: The history of this family is rather exasperating. The 

 original genus Holothuria of Linnaeus, listed in the 10th edition with 

 four species, is based on some of the large siphonophores, such as Phy- 

 salia, as was pointed out by T. Gill in Science, 1907, p. 185, in 

 a critical attack on W. K. Fisher. The latter {ibid., p. 389) admitted 

 the correctness of this fact, but posed the question of what to do with a 

 name which has been as well established as the word "mammal," and 

 how to get around the use of the word Holothurioidea, etc. Linnaeus' 

 name was at first accepted as the name for all the common tropical 

 aspidochirotes ; but in the course of time the most characteristic forms 

 were segregated under new generic names, and various writers strove to 

 arrange the remaining large number of species in a more or less natural 

 order, using the distribution of the feet, the spicules, and other features. 

 In these efforts they were greatly handicapped by the incompleteness of 

 the earlier descriptions. 



In 1914 Pearson attempted to subdivide the large genus Holothuria 

 on the basis of his knowledge of a very limited fauna, that of Ceylon. 

 Unfortunately he selected the poorest, most artificial of all systems, that 

 of Brandt, with its many useless generic names — useless because in many 

 cases one cannot recognize the species he describes and in others his 

 definitions are so broad that almost any species could be included in the 

 genus. Pearson's system has more or less been adopted by Heding and 

 Panning. To the latter we are indebted for a most careful revision of 

 the genus Holothuria, as well as Bohadschia and Actinopyga; for some 

 reason he did not include the small genus Labidodemas. 



Panning included about 120 species in Holothuria s. /., subdivided 

 into smaller groups which unfortunately are not clearly defined. Of 

 these species, about 40 can either be withdrawn as synonyms of 

 well known forms or are so incompletely described that they must be 

 rejected. About 80 species remain. Twenty are here reported from the 

 Panamic region, plus Mertensiothuria platei, from Juan Fernandez, 

 which possibly may be found to range into the region under discussion. 

 Two of these species were not included in Panning's report, and one of 

 them is new. 



