86 The Genera of the Plumulariidce, 



usual, but spring from the stem supporting the calycle 

 between the latter and the sarcotheca;" and he adds that "in 

 some cases after reaching a certain height they give origin 

 to a second calycle similarly placed;" and he consequently 

 concludes that they are modified ramuli, in which case the 

 species would come under the genus Lytocarpus, as herein 

 restricted. 



Aglaophenia, LamouToux, modified. 



Hydrocladia pinnately arranged, mesial and lateral 

 sarcothecEe attached to the hydro theca for at least a part of 

 their length. 



Gonangia produced in a corbula, the rachis of which is a 

 modified hydrocladium, and the ribs modified mesial 

 sarcothec£e, often united to form a closed sac. 



According to the above definition the genus will include 

 all the true corbula-bearing species which Professor Allman 

 ranks under Lytocarpus. I have taken for granted the 

 correctness of Professor Allman's theory of the origin of the 

 corbula. According to this view the hydrothecse of the 

 gonangial pinna become, in certain species, turned alternately 

 to the right and the left, and raised above the pinna on 

 peduncles, and it is the mesial sarcothecaB of these hydro- 

 thecse which, becoming enormously enlarged and developing 

 a number of secondary sarcothecse, constitute the ribs of the 

 corbula. Mr. Fewkes' objection that this view assumes tlie 

 existence of two series of hydrothecte side by side on the 

 gonangial pinna is based on a misconception, as the pinna 

 consists only of a single series of internodes with a hydro- 

 theea on each, though the fact of the hydrothecEe being 

 turned alternately to right and left gives them the appearance 

 of being biserial. It is an easy transition to such species 

 as A. divaricata, which l^ve the hydrothec^e of the corbula 

 entirely suppressed ; and, whether the hydrothecge be absent 

 or not, the ribs may be represented by broad leaflets, and 

 united to form a pod. Such species as A. divaricata have 

 the secondary sarcotheca of the narrow corbula-ribs in 

 distinct pairs, and usually very much larger than those 

 which border the broad leaflets of A. parvula and its 

 allies. 



Of the Australian species whose gonosomes are known^ 

 those which have an open corbula, with numerous narrow 

 ribs, like those of A. acanthocarpa (Allman), are A. divari- 



