NO. 2 DEICHMANN : HOLOTHURIOIDEA ; PART II, ASPIDOCHIROTA 283 



The material discussed here is divided into 13 genera, which take in 

 the majority of the known species. Whenever possible, all the species 

 referred to a genus have been included in the key ; in other cases a tenta- 

 tive list is given of the species which probably should be referred to the 

 genus. As for the genus Holothuria L., which has no right to exist, one 

 might abandon it completely, using the name as a colloquial term, like 

 "amphioxus," which covers all lancelets; or one might select as its type 

 one of the oldest and best known species from the Mediterranean, such 

 as Holothuria poll delle Chiaje, which possibly may have been the form 

 Aristotle had in mind when he gave the first description of these ani- 

 mals. 



Key to the genera of the family Holothuriidae from the 



Panamic region 



1. Skin gelatinous, soft. Appendages restricted to the ambul- 

 acra, not numerous. Calcareous ring unusually low and deli- 

 cate with almost ribbonlike interradialia. Spicules tables, not 

 numerous, and in some species a few buttons, usually twisted 

 and incomplete, suggesting clumsy C-shaped bodies. Color 

 white or golden brown, mostly with darker appendages. 

 1. Labidodemas Selenka 



1. Skin not gelatinous, soft. If appendages restricted more or 

 less to the ambulacra, the spicules numerous. Calcareous spi- 

 cules variously developed, rarely with tables completely lack- 

 ing; and in that case spicules of other forms — rods, buttons 



— present in the inner layer 2 



2. Skin with few to many spicules, never rigid from being 

 packed with spicules 3 



2. Skin parchmentlike, stiff, packed with spicules. Burrowing 

 forms 11 



3. Tables forming a close outer layer. Disk usually lacking; 

 spire tall, ending in a few strong spines, forming a Maltese 

 cross when seen from above. Inner layer lacking, or consisting 

 of scattered huge, flat bars. Slender form, cylindrical or 

 bottle-shaped, with small terminal tentacles. Under rocks. 

 (languens group) .... 6. Semperothuria n. gen. 



3. Tables variously developed but not forming a crowded outer 

 layer and not lacking the disk. If tables lacking or rare, a 

 deeper layer of rods, buttons or rosettes is developed. . . 4 



