REPORT ON THE HYDROIDA. 49 



Gonosome not known. 



In the external ealyx-like duplicature of the hydrotheca walls of the remarkable 

 Plumularian ou which the genus Diplocheilus has been founded, we have a character 

 which is absolutely unique among known Plumularians. A scarcely less exceptional 

 character is found in the absence of lateral nematophores, and in the reduction of the 

 mesial nematophore to a sessile, shield-like process unconnected with the hydrotheca. 



Diplocheilus mirahilis, n. sp. (PI. VIII. figs. 4-7). 



Tvophosome. — Colony attaining a height of two or tliree inches, sparingly branched ; 

 stem monosiphonic, divided into internodes by oljlique joints ; hydrocladia about two- 

 tenths of an inch in length, having their internodes separated by very oblique joints. 

 Hydrothecae widening from lielow upwards, and with the margin everted ; mesial 

 nematophore very short and wide, forming a concave shield-like process, with a central 

 perforation at a short distance lielow the hydrotheca. 



Gonosome not known. 



Diploclieihis mirahilis presents unmistakable points of affinity with both Eleuthero- 

 plean and Statoplean Plumularidse. To the Statoplcan forms it is connected by its fixed 

 nematophores, and this character is presented not only by the mesial nematophore of the 

 hydrothecal internode, but by certain cauline nematophores which are developed on the 

 internodes of the stem. To the Eleutheroplea it shows an affinity by the non-serrated 

 margin of its hydrotheca, and by the very oblique joints which separate the internodes 

 of the hydrocladia, a character which specially recalls a similar condition in the Catharina 

 group of the Eleutheroplea. 



Its position among the Statoplean rather than among the Elcutheroplean Plumularidse 

 must be regarded as decided by the entire absence of moveable nematophores. 



Diplocheilus mirahilis — the only knowTi species of its genus — is represented in the 

 collection only by a fragmentary specimen. 



Dredged at Station 162, April 2, 1874, off Moncceur Island, Bass Strait; depth, 

 38-40 fathoms; bottom, sandy. 



Cladocarpus, AUm. 

 Cladocarpus, Allman, Trans. Zool. Soc. Lond., vol. viii., 1873. 



Generic Character. Trophosome. — A simple or branched hydrosoma, with pinnately 

 disposed hydrocladia. 



Gonosome. — Gonangia not included in corbulse, or protected by any other form of 

 modified hydrocladium, but borne on the sides or at the base of special protective branches, 

 wliieh are appendages of the hydrocladia. 



(zool, CH41jL. E^vP. — FART XX. — 1883.) U 7 



