Species of Echinonematous Sponge. 47 



abruptly bent acuate, sharply pointed at one end and merely 

 rounded off at the other. In P. clopetaria, O. S., a fat 

 clumsy tuberculated spicule is said to be characteristic, and 

 travesties rather than represents our echinating acuate. 



As regards the affinities of the genus, O. Schmidt considers 

 it related on one hand to the Suberites, and on the other 

 to the genus Clathria. That it is a true echinonematous 

 sponge (»". e. allied to Clathria) there is no doubt ; and cer- 

 tainly the spicules of the axial column and lower part of the 

 base are arranged in a very suberitic fashion. The scopi- 

 form bundles of acuates in the intermediate layer remind one 

 of Microciona ; and if one added to the membranous base of 

 the latter a layer of felted spicules, the resemblance would 

 become almost complete, especially as Myxilla, which in at 

 least some of its species is identical with Microciona, fre- 

 quently grows upwards into stalked processes, which appear 

 to resemble those of P. plena. 



In the relation of the scopiform bundles of spicules to the 

 axial columns of the sponge, Plocamia shows some similarity 

 to Dictyocylindrus ramosus, Bwk. ; but the latter has not the 

 spicular dermal layer which occurs in the former. In Phakellia 

 the dermal layer is present, but the scopiform bundles are re- 

 placed by long plumose fibres. Thus the affinities of the sponge 

 are all with Echinonematous forms ; and it should apparently 

 be referred to the family Ectyonidas, where it will form a 

 group by itself, viz. the Plocamianina, with the following defi- 

 nition : — Sponge growing proliferously upwards from an 

 incrusting base ; skeleton consisting of axial columns of dumb- 

 bell-headed spicules supporting scopiform bundles of large 

 acuates, which, as well as the axial columns, are echinated by 

 smaller acuates of another form, the exterior provided with a 

 dermal spicular covering, and the sarcode containing very 

 minute flesh-spicules. 



Order ECHINONEMATA, Carter. 



Family Ectyonidae, Carter. 



Group Plocamianina, Sollas. 



Genus Plocamia, O. Schmidt. 



Species: 1. Phcamia gymnazusa,Q. S. 



2. Plocamia clopetaria, O. S. 



3. Plocamia plena, Soil. 



It is worthy of notice that no horny material is discoverable 



