XO. 3 DEICHMANN: HOLOTHURIOIDEA ; PART I, DENDROCHIROTA 123 



circle of smaller tentacles was completely missed by Semper and the spe- 

 cies therefore likewise referred to Thyone.^ The genus resembles the 

 northern genus Thyonidium but is distinguished by the almost completely 

 resorbed interradials. As Eucyclus is preoccupied, a new genus had to be 

 established. 



Key to the Genera of Phyllophoridae Known from the 

 Panamic Region and Chilean Waters 



All the genera known from this region have at utmost 20 tentacles, 

 and the feet are numerous in the interambulacra as in the genus Thyone. 

 1. Tentacles distinctly of 2 sizes, i.e., 10 large ones in the external 

 circle and either 5 small ones, more or less deeply divided, or 5 

 small pairs of equal size in the inner circle 2 



1 . Tentacles of varja'ng number and size, sometimes of almost the 

 same size; the 2 circles are more or less confluent 3 



2. Calcareous ring low, simple (or with insignificant posterior 

 projections) ; interradials well developed, often pentagonal or 

 heart-shaped — in many cases overlapping the radials. Spicules 

 derived from 2- to 4-pillared tables, often reduced to plates 

 with 2-4 knobs or spines indicating the pillars. Feet with end 

 plate but no supporting tables, sometimes a few rods. Tentacles 

 with rosettes and delicate rods. 1. Euthyonidium Deichmann p. 124 



2. Calcareous ring low, simple; radials with long anterior tooth, 

 interradials completely vestigial, easily overlooked. Spicules 

 apparently lacking except for the end plate and a few branching 

 rods 2. Athyonidium, new genus p. 127 



3. Calcareous ring simple ; radials tall, posteriorly slightly incised ; 

 interradials well developed. Spicules almost totally lacking, 

 except for end plate and a few perforated plates. Tentacles 20, 



large, of almost equal size. Large reddish species 



3. Pattalus Selenka p. 129 



3. Calcareous ring with long posterior prolongations. Tentacles 

 of different size, fairly delicate. Spicules 2- to 4-pillared tables 

 sometimes scarce in older individuals. Small- to medium-sized 

 forms 4. Phyllophorus Grube p. 132 



6 In other specimens Semper noticed the inner circle of smaller tentacles and 

 these he referred to Pattalus with a comment on the variability of the tentacles in 

 this genus. 



