167 



Fis. 4. 



Fiff. 5. 



developing in the body cavity as in Synapta vwipara and Chiridota 

 rotifera. The largest of the 3 individuals before me contained 10 young, 

 the smallest of which is 2 mm in length the largest 7 mm. The former 

 has 5 tentacles well developed and the alternating 5 are just appearing. 

 The latter has 10 tentacles which have begun to branch. The other 

 young ones are at various intermediate stages of development. In all 10, 

 the calcareous ring is well developed but there are prominent anterior 

 prolongations instead of posterior. None of the young have any pig- 

 ment in the body wall. The smallest individual has no pedicels and 

 only the first signs of a few calcareous particles. In a specimen 3 mm 

 long, the pedicels of one ambulacrum have begun to appear. In the 

 largest individual the body-wall is full of knobbed buttons and tables 

 like those of the adult, and there are a dozen or more pedicels in each 

 ambulacrum. There are 

 also 5 prominent anal 

 teeth. Besides these 

 specimens already re- 

 ferred to there are in the 

 collection, 2 smallHolo- 

 thurians, 7 and 1 4 mm 

 long respectivlly, pvire 

 white in color and with 

 thepedicels confined to 

 the ambulacra, which 

 have calcareous par- 

 ticles similar to those of 



this species and I presume they are the young, taken not long after birth. 

 If that is the case, the young in this species are born when about one- 

 third the length of the mother ; they are then white and have the pe- 

 dicels confined to the ambulacra; the color and increased number of 

 pedicels are acquired with age. 



But by far the most interesting Holothurian from California is a 

 curious little species which fails to fit into any known genus and for 

 which therefore I have formed the new genus Thyonepsolus. The ori- 

 gin of this name is obvious; it is suggested by the Psolus-Vike appear- 

 ance of the animal combined with the Thyone-V(ke character of the 

 dorsal side. The description follows : 



Thyonepsolus nov. gen. Tentacles 10. Ventral surface flattened to 

 a sharply defined creeping sole on which the pedicels are arranged in 

 3 longitudinal series. Dorsal surface arched, covered with a very thick 

 soft, loose skin and with numerous pedicels scattered quite uniformly 

 over it. Mouth anteriorly, anus posteriorly, placed on dorsal side, 



