AND SPECIES OF HYBKOIDA. 275 



tophore — a character in wliicti it agrees with Kirchenpauer's sub- 

 genus Macrorynchia, with which it further agrees in the fact of 

 this free portion of the mesial nematophore being provided not 

 only with a terminal orifice, but with the lateral one to which 

 Kirchenpauer first drew attention as occurring in those forms 

 which he united in his subgenus Macrorynchia. The species, how- 

 ever, included by Kirchenpauer in this subgenus have a gonosome 

 very different from that of the present species, the gonangia of the 

 MacroryncJilfS being unprotected by corbulaj, and merely sup- 

 ported on the surface of more or less modified pinnae. 



But the most strildng feature of Aglaophenia acanthocarpa 

 will be found in its beautiful corbulae. The leaflets which form 

 the walls of the corbula are free in their entire length, and carry 

 along their opposed edges opposite pinnately disposed nemato- 

 phores, each in the form of a blunt spine, and having both a ter- 

 minal orifice and, close to its base, a lateral one, exactly as in the 

 mesial nematophores of the hydrothecae. The longest leaflets, 

 which are situated near the proximal end of the corbula, carry 

 about eleven pairs of nematophores ; the shortest, which are at the 

 distal end, carry usually from five to seven pairs ; each leaflet, 

 moreover, has a transverse joint between every pair of nemato- 

 phores, and at its base carries upon one side two nematophores, 

 which spring, by a common root, from the basal joint of the 

 leaflet. 



This double nematophore is especially interesting in a homo- 

 logical point of view ; for it represents the two lateral nemato- 

 phores of a hydrotheca, the mesial nematophore being represented 

 in a greatly modified form by the leaflet itself, and the hydrotheca 

 being entirely suppressed. 



The sliort stalk by which the corbula is attached to the stem 

 carries a single hydrotheca. 



Aglaophenia laxa. Plate XXT. figs. 5-7. 



Trophosome. Stem attaining a height of about two inches, fasci- 

 cled below, irregularly or subalternately branched ; branches all 

 lying in the same plane, divided into rather long internodes, each 

 internode carrying a pinna ; pinnse distant, each supported on a 

 short process, which springs from the latero-anterior aspect of 

 the hydrocaulus. Hydrothecse approximate, rather deep, gra- 

 dually widening upwards, margin deeply toothed, with the second 

 tooth from the front everted; intrathecal ridge strong, situated 



LINN. JOUKN. — ZOOLOGY, VOL. XII. 20 



