THE APODOUS HOLOTHURIANS 87 



aoter which he gives for Chiridota.) It is necessary, therefore, even if it is dis- 

 agreeable, to change Ostergren's selection and nse Verrill's {'67) name Lep- 

 tosynapta for these forms of which inlKerens is typical. The species S. bachei 

 Ayres is an absolute noinen nudum, without a word of description or explana- 

 tion. It is possibly a Chiridota. 



The genus as now restricted includes nine species, of moderate or small 

 size, all but one of which occur in the north temperate zone, though some of 

 them range southward into the warmer seas of the tropics, while others occur 

 in the cold waters of the far north. They live in sand or mud, usually burrow- 

 ing like worms and feeding on the organic matter which they pick out of the 

 dirt with their tentacles; but they are continually taking in grains of sand and 

 other indigestible stuff with the food, so that the alimentary canal is usually 

 filled with such material. They are sluggish in their movements and apparently 

 come out of their burrows only on rare occasions, though they are sometimes 

 found (particularly roseola) under rocks and in similar situations. 



Key to the Species op Leptostnapta. 



A. — Tentacles 12; lengtli usually over 50 mm. 



B. — Eadial pieces of calcareous ring perforated for passage of the nerves (pi. v, fig. 14). 

 C. — Anchors and plates of variable size, but of only one kind. 



D. — Anchors usually under 250 ;u, never over 300 /x; plates more or less oval, 

 with smooth margins and not more than 7 or 8 dentate holes. 

 E. — Anchor-plates more or less symmetrical, with distinctly dentate holes, 

 more than 125 ix long in posterior part of body and much more 

 than half as long as anchors there. 



Anchor-arms usually with 4 or more teeth ; calcareous particles in 

 longitudinal muscles, oval or dumb-bell-shaped; radial pieces 

 of calcareous ring decidedly concave on the posterior edge ; polian 



vessel usually single inh^Rens 



Anchor-arms with only 2 or 3 small teeth; calcareous particles in 

 longitudinal muscles C- or doughnut-shaped; radial pieces of 

 calcareous ring scarcely concave posteriorly ; polian vessels 3-7. 



dolabrifera 



EE. — AnchoT-plates more or less unsymmetrical, with the holes smooth or 



with few teeth, less than 125 /x long in posterior part of body and 



only a little more than half as long as anchors there ooplax 



DD. — Anchors usually over 250 /a and often over 500 ;a; plates elongated, with 

 more or less dentate margin and often more than 8 dentate holes. 

 Anchors not often over 500 ,x; plates with 7 to 30 holes, .galliennii 

 Anchors 500 to 800 /x; plates usually with 25 to 40 holes. 



MACRANKYRA 



CO. — Anchors and plates of two quite distinct kinds (pi. v: figs. 1-4) ; polian vessels 



2-5 ACANTHIA 



BB. — Eadial pieces of calcareous ring not ])erforated, but simply notched, for the passage , 



of the nerves (pi. v, fig. 16) roseola 



A.4.— Tentacles 10; length 3-50 mm. 



Tentacles with digits ; length 30-50 mm decaria 



Tentacles without digits ; length 3-5 mm mindta 



