SO-CALLED MOLLUSCOIDEA 



28s 



Class Phoronoidea 



This class was erected for the genus Phoronis, which has been 

 associated both with the Gephyrea and with Polyzoa. Another genus 

 Phoronopsis, from the Cape, has been recently established. It has 

 been proposed to associate these two genera, along with Cephalodiscus 



CNR 



Fig. 153. — Actinotrocha or 

 larva of Phoronis. — After 

 Masterman. 



The mouth is overhung by the 

 prominent pre-oral hood ; the 

 anus is at the other end of the 

 body. Behind the mouth is a 

 ring of ciliated tentacles. 



SP., the nerve ganglion in the 

 hood ; N.G., the nerve gan- 

 glion of the region called collar 

 region by Masterman ; CNR., 

 nerve-ring at base of tentacles. 



Fig. 154. — Phoronis, much 

 enlarged. 



TR., Trunk ; TE., tentacles ; TU., tube. 



and Rhabdo pleura, with the Hemichorda, on account of certain Chordate 

 affinities said to be exhibited by the larva. But the evidence for this 

 is very unconvincing. 



The genus Phoronis includes a few species of small marine " worms," 

 social in habit, and found enclosed in fixed leathery tubes often en- 

 crusted with foreign particles. Each individual is furnished with a 

 horseshoe-shaped crown of tentacles, which are hollow and supported 



