MADREPORAEIAN FAMILY — THE PUlSTGIDiE. 155 



very curious small and numerous synapticula, wliicli, however, 

 can be clearly differentiated from ornament. 



Finally, the columella is trabecular, and in some places, where 

 large septa come close together, on opposite sides of the axial 

 space, it appears to unite them together. It is partly formed 

 by growths from their joined inner edges, and partly from struc- 

 tures of a trabeculate nature which spring from the original base 

 of the young corallum. 



Part IV. The Construction of Halomitra Crustacea, Rumphius sp. 



G-enus Halomitea, Dana, 1816. — Fungia, pars. — Podabacia, 

 Milne- JEchmrch Sf Jules Saime^ 1850. 



There are two genera of the Funginae, according to Milne- 

 Edwarda and Jules Haime, which are very closely allied, namely 

 Podahacia and Halomitra. Halomitra was founded by Dana in 

 1816, and Podahacia by Milne-Edwards and Jules Haime in 

 1850. 



Halomitra, a well-defined genus, included a species which had 

 been differently named by Eumphius, Maratti, Lamarck, and 

 most of the writers on Corals before 1824. It is evidently one 

 of the Funginae, as it has a perforate base ; and it departs from 

 the configuration of the species of Fimgia and Herpolitha by 

 being compound, and by not having a long axial space and irre- 

 gularly placed and rather indefinite calices. 



Podahacia includes a species described by Dana and placed 

 under the genus Pavonia, Lamk. ; yet all the distinctions between 

 the genera Halomitra and Podahacia are that the solitary species 

 of the last is fixed and not free, has the base finely granular, the 

 granules being sharp and spiny, and the smaller calices are sub- 

 radiate. So that between it and Hdlomitra with a free corallum, 

 tolerably distinct calices, and large papillae on the base there is 

 not a generic difference. Both groups have a large calice around 

 which smaller ones are concentrically arranged. 



MM. Milne-Edwards and Jules Haime state (op. cit. vol. iii. 

 p. 20) that Halomitra is " tres voisin du precedent {Podahacia), 

 dont il ne differe que par sa forme generale et la liberte de 

 sa base." I therefore unite the genera, and give the name Halo- 

 mitra to the conjoined forms, it having precedence from age. 



Halomitra Crustacea, a species named Madrepora Crustacea by 

 Pallas, is the type I have examined ; and the specimen came from 



