REPORT ON THE HYDROIDA. 49 
Gonosome not known. 
In the external calyx-like duplicature of the hydrotheca walls of the remarkable 
Plumularian on 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 mirabilis, n. sp. (Pl. VIII. figs. 4-7). 
Trophosome.—Colony attaining a height of two or three inches, sparingly branched ; 
stem monosiphonic, divided into internodes by oblique joints; hydrocladia about two- 
tenths of an inch in length, having their internodes separated by very oblique joints. 
Hydrothecee widening from below 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 below the hydrotheca. 
Gonosome not known. 
Diplocheilus mirabilis presents unmistakable points of affinity with both Eleuthero- 
plean and Statoplean Plumularidz. ‘To the Statoplean 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 
eroup of the Eleutheroplea. 
Its position among the Statoplean rather than among the Eleutheroplean Plumularidee 
must be regarded as decided by the entire absence of moveable nematophores. 
Diplocheilus mirabilis—the only known 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, Allm. 
Cladocarpus, Allman, Trans. Zool. Soe. Lond., vol. viii., 1873. 
Generic Cuaracter. Zvrophosome.—A simple or branched hydrosoma, with pinnately 
disposed hydrocladia. 
Gonosome.—Gonangia not included in corbule, or protected by any other form of 
modified hydrocladium, but borne on the sides or at the base of special protective branches, 
which are appendages of the hydrocladia, 
(ZOOL. CHALL, EXP.—PART xx.—1883.) LUE 7; 
