THE APODOUS HOLOTHURIANS 17 



Chiridotinae without wheels, but with small C- or bracket-shaped bodies. It is 

 thus very closely allied to Chiridota. The genus Trochodota is a natural group, 

 well characterized by several morphological features. At first sight it might 

 seem that Ludwig's name is antedated by Studer's Sigmodota, but although 

 Studer states that his type species is Lesson's purpurea, a perfectly recog- 

 nizable species which Ludwig makes the type of Trochodota, he incorrectly 

 identified the Chiridotinse before him and in spite of their having 12 tenta- 

 cles, called them purpurea; consequently he states that Sigmodota has 12 

 tentacles. (It has been generally assumed that he says further there are 

 no wheels in Sigmodota; as a matter of fact, he says nothing whatever 

 on that point.) Ludwig ('986) has shown that the species Studer had in hand 

 was undoubtedly Chiridota contorta Ludw., and as his generic diagnosis fits that 

 species, contorta becomes the type of Sigmodota. But even though it is thus 

 clear that Sigmodota and Trochodota are not synonyms, the former name can- 

 not be used; for in 1868 Semper suggested that the peculiarities of Chiridota 

 australiana Stimpson warranted its being made the type of a new genus to 

 which he gave the name Tseniogyrus. This seems to be a natural and acceptable 

 course to follow ; but the genus, which is characterized by the presence of wheels 

 collected in papillae and numerous scattered sigmoid bodies, includes besides 

 the type-species, C. contorta Ludwig and consequently Sigmodota Studer is a 

 synonym of Taeniogyrus Semper. The interesting species, C. japonica v. Mar- 

 enzeller, bears the same relation to Taeniogyrus that Toxodora does to Chiri- 

 dota, and therefore is best treated as the type of a new genus, Scoliodota (see 

 page 125). There are still left about a dozen species to make up the genus Chiri- 

 dota, but one of these, the widespread C. rufescens Brandt, is so distinct from 

 the others that it is entitled to generic rank, and we may call the genus Poly- 

 cheira (see page 120). It is clear, I think, that Anapta inermis Fisher is one 

 of the Chiridotinae, and must, therefore, be made the type of a new genus which 

 may well be called Achiridota (see page 126). There are thus seven genera of 

 Chiridotinas which it seems proper to recognize, instead of the two given by 

 Ostergren. However much multiplicity of genera is to be deplored, it cannot 

 be avoided in this subfamily if our classification is to show natural relation- 

 ships. In the Myriotrochinae there are three well-marked genera, univer- 

 sally recognized, based on the form of the calcareous wheels; Myriotrochus, 

 with wheels having 10-25 spokes and 17-35 large teeth extending horizontally in- 

 ward from the rim ; Trochoderma, with wheels having 10-16 spokes, and the rim 

 with large, scattered, sharp knobs, but no horizontal teeth; Acanthotrochus, 

 with two distinct kinds of wheels. 



Turning now to the Molpadiidae, we are confronted by only about half as 

 many species as in the Synaptidae, but with even more difficulty in arranging 

 them in genera. No suggestion of subfamilies needs consideration in this 



