136 BULLETIN OF THE 



rising above the orifice of the hydrotheca. Mesial nematophore single, adnate, 

 extending only a short distance up along the face of the hytbotheca. 



Gonosome : — Phylactogonia springing from the proximal iuternodes of pinnae- 

 on opposite sides of the stem. Number of phylactogonia twenty. Each phy- 

 lactogonium with three branches formed by two bifurcations. The first of 

 these bifurcations situated near the origin of the phylactogonium. Each branch 

 of the phylactogonium bears a single row of nematophores. 



Gonangia affixed to the main stem and protected by the branching jjhylacto- 

 gonia. 



This species resembles closely G. ventricosus, Allman. A bottle of type 

 specimens contains the hydroid figured by him, PI. XXXI. fig. 1, and frag- 

 ments which resemble C. compressus. 



In C compressa the margin of the hydrotheca is simply toothed, and there 

 is no prominent medially placed single spur as is found on the rim of the 

 hydrotheca in C. ventricosus (Allman, PI. XXXI. fig. 1). The hydrotheca is 

 not ventricose, as in C. ventricosus, and the whole trophosome is smaller. 



St. Vincent, 114 fms. 



PLEUROCARPA, n. g. 



The characteristic of this genus is a peculiar gonosome, which is formed 

 from the proximal portion of a branch, while the distal end of the same retains 

 the true character of the branch and bears pinnoe. Gonosome a corbula. 



Pleurocarpa ramosa, n. s. 



Hydrosome: — Hydrocaulus branching, eight to ten inches high. Stem 

 stout, non-fascicled. The branches bear medially placed rows of nemato- 

 phores. Pinnae jointed, alternate, arise from upper surface of the branches. 

 Hydrothecae closely approximated on the pinna, short, thick, margin toothed. 

 Intrathecal ridge prominent. Mesial nematophore in distally placed hydro- 

 thecae, adnate along the whole face, and continued beyond the orifice of the 

 hydrotheca. In proximal hydrotheca;, however, although adnate along the face 

 of the hydrotheca, the mesial nematophores seldom rise above the margin. 



Gonosome : — Corbula open, formed by many rib-shaped pinnae on the prox- 

 imal end of a branch. Each rib is destitute of hydrothecae, and covered with 

 tubular nematophores, which project at right angles to the axis of the rib from 

 all sides. Proximal end of the branch of which the corbula is a modification 

 destitute of pinnae, forming a peduncle for the gonosomes. It bears several 

 hydrothecae. The Ijranch beyond the corbula bears many alternately arrange<l 

 pinnae, with hydrothecae, not unlike a normal branch of the trophosome. 



St. Vincent, 95 fms. 



This genus proves without doubt that the structure called a corbula is in 

 some cases a modified branch, and not, as Allman has shown to be true 

 in some genera, a modified pinna. According to Allman, the ribs of the 



