478 PEOFESSOE G. J. ALLMAN ON THE HTDEOIDA 



thecal ridge. Nematophores fixed ; lateral nematophores, one on each side of the orifice 

 of the hydrotheca ; mesial nematophores usually adnate for a greater or less extent to 

 the front of the hydrotheca, occasionally free. 



Gonosome. — Gonangia not included in corbulse, but borne on the sides or at the base 

 of special protective branches, which are appendages of the pinnse. 



I have constructed the genus Cladocarjms for a group of Plumularidse in which the 

 proper hydrothecse-bearing pinnae carry peculiar branching appendages (Plate LXVIII. 

 fig. 1", a, a), which are destined to support the gonangia or in some other way to afford 

 protection to them. 



These appendages differ essentially from the open and closed corbulse of other forms 

 in the fact that they are not, like corbulse, metamorphosed pinnae, which take the place 

 of unaltered pinnae, but appendages superadded to the pinnae. 



In Kirchenpauer's subgenus Macrorhynchia, the gonangia are also borne on special 

 branches (gonocladia and nematocladia, of Kirchenpauer) ; but these are always, as in 

 the true corbulae, metamorphosed pinnae. 



MacrorhyncMa is further distinguished from Cladocarpus by the form of its mesial 

 nematophores. which are veiy long, usually far surpassing the height of the hydrotheca, 

 and which, as Kirchenpauer first pointed out, are always provided with a lateral as well 

 as a terminal orifice after they cease to be adnate to the hydrotheca. 



It will be seen that the genus Cladocarpus is nearly allied to Aglaophenia. With 

 this genus it is coincident so far as regards its trophosome ; but it differs from it in its 

 gonosome, which is not provided with corbulse, and instead of these receptacles has special 

 ramuli, which are appendages of the pinnae and are destined for the protection of the 

 gonangia. Its connexion with Aglaopheiiia is maintained through the forms included by 

 Kirchenpauer in his subgenus Maci'orhynchia. 



Cladocakpus formosus. Plate LXVIII. figs. 1, 1°, 1*. 



Trophosome. — Stem attaining a height of between two and three inches, slightly re- 

 curved, simple, or with some small branches given off from its anterior aspect, fascicled 

 below, pinnae alternate, jointed, each joint supporting a hydrotheca, pinnae near the centre 

 of the series about three quarters of an inch in length, and thence decreasing in length 

 upwards and downwards. Hydrothecae nearly cylindrical, with the margin provided 

 with short teeth ; mesial nematophore forming a stout spine extending to about half 

 the height of the hydrotheca, to which it is adnate for the greater part of its length, 

 becoming free at a short distance from its summit ; lateral nematophores forming short 

 blunt conical processes, slightly rising above the margin of the hydrotheca. Main stem 

 (rachis) giving off minute nematophores, which are disposed in more or less regular 

 verticils. 



Gonosome. — Gonangia-bearing ramuli springing each from the basal joint of a pinna, 



