84 MR. P. H. CAEPEXTEE OX THE GENUS ACTINOMETRA. 



one of these axial interradial canals is indicated, in PI. V. fig-. 11, by a brown bristle (II) 

 which has been passed along it. 



In the type of Act. polymorpha the distal faces of the radial pentagon are placed 

 somewhat more vertically than in Act. Solaris, so that scarcely any trace of the muscular 

 fossae is to be seen on its ventral aspect (PL VI. fig. 5). This is still more the case in 

 var. 4 (fig. 23), in which the ventral aspect of the radial pentagon exhibits nothing but 

 the extremely sculptured and inclined ventral faces of its component pieces ; it is divided 

 into a very large number of ridges and farrows, nearly every one of the latter having a 

 canalicular ojiening into the central network (c.n). The radial furrows arc thus entirely 

 obliterated; and as there is no corresponding intermuscular furrow on the distal face 

 (as in Ant. celtica, PI. IV. figs. 4, 6), there is nothing to indicate their position on the 

 outer margin of the radial pentagon. But the interradial furrows (PI. VI. fig. 12, v.i.f) 

 are readily distinguishable by their being somewhat deeper and straighter than the 

 secondary radial furrows. This is also the case, but to a less extent, in the type (fig. 5) 

 and in varieties 2 and 3 ; but var. 1 is somewhat different, and in this respect approaches 

 Antedon rosacea more than any other Actinometra with which I am acquainted. The 

 distal faces of the radial pentagon (PI. VI. fig. 12) are perceptibly inclined to the 

 vertical axis of the calyx, so that even the opening of the central canal (c.c) appears on 

 its ventral aspect. The muscular fossae (/) are deep, so that their superior margins 

 project inwards and encroach somewhat on the ventral faces ; and the median furrows 

 of the latter are tolerably deep, their outer extremities passing over into the inter- 

 muscular furrows (f) of the distal faces. The interradial furrows between the elevated 

 lateral halves of the ventral faces (PI. VI. fig. 12, v.i.f) are also deep, but the ventral 

 faces are plain and scarcely at all sculptured, so that both radial and interradial furrows 

 pass down with tolerable regularity into the peripheral axial canals of the central cal- 

 careous network (c.n). 



(§ 57) In Antedon rosacea, as we have already seen, the five radial diverticula of the 

 ccelom terminate blindly on the ventral surface of the centrodorsal piece in five depres- 

 sions (PI. IV. fig. 15, q), which are disposed around the opening of its central cavity (ccl.c). 

 In correspondence wdth these depressions the dorsal surface of the pentagonal base pre- 

 sents five large openings (PI. IV. fig. 16, Q), disposed in like manner around the margins 

 of its central space. These openings are the dorsal terminations of the five radial axial 

 canals, and are formed by the application of the five radial spout-like processes of the 

 rosette (figs. 13, 16, p) to the inflected margins of the two openings (.(•', y) on the internal 

 face of each first radial (fig. 12 c), through which the secondary basal cords (X, 1\) pass 

 on their course from the fibrous mass enveloping the quinquelocular organ to the 

 circular commissure contained within the radial pentagon (compare PI. VIII. fig. 2). 



The existence of these five large openings (PL IV. fig. 16, Q) is due to the fact that the 

 dorsal face of each first radial presents a deep notch in the centre of its inner margin 

 (fig. 12 b, Q') ; this notch indicates the continuation towards the dorsal surface of the 

 radial axial furrow on the internal face (fig. 12 c, a.r.f) ; and when this furrow becomes 

 converted into a canal by the application to its inflected edges of one of the spout-like 

 processes of the rosette, the notch on the dorsal face also becomes converted into a cir- 



