140 THE VOYAGE OF H.M.S. CHALLENGER. 



Genus Pteropathes, n. gen. 



The polyps are arranged in a single linear series confined to one aspect of a branch. 

 They are so closely crowded that there is no ccenenchyma on the zooidal surface of the 

 axis, and the line of demarcation between two adjoining polyps passes straight across. 

 In front view the polyps have a rectangular outline, and an elongation in the transverse 

 axis is never marked. The tentacles are fleshy fusiform processes, but frequently in 

 spirit preparations become much contracted. They are arranged in pairs, the two lateral 

 pairs being parallel to one another and rather near together, though not so close as in 

 the genus Aphanipathes. The sagittal tentacles are inserted at a very much lower level 

 than the others, and are often not visible from the anterior surface. The peristome is 

 relatively flat around the mouth, and the lateral tentacles spring from it. The sagittal 

 tentacles, however, are inserted at a point opposite the centre of the sclerobasic axis, and 

 between them and the margin of the peristome there is a deep cleft. The sagittal tentacles 

 when fully developed are rather larger and thicker than the others, but in spite of this fact 

 they are the earliest to atrophy. Polyps with only four tentacles are of frequent occur- 

 rence. The stomodseum is elongated in the sagittal axis, and the ectoderm clothing its 

 inner wall is thrown into irregular folds. These usually become elongate tubular processes 

 at a little distance below the oral aperture, and have a lumen opening into that of the 

 stomodseum. The convolutions of the stoniodseum occupy a position which, in the main, 

 is parallel to the sagittal axis of the polyp, and are sometimes more complex at one 

 extremity of the stomodseum than at the other. The reproductive elements are contained 

 in specialised bands of cells attached to the stomodasum and body-wall, and occupy 

 almost the whole of the ccelenteron. The only known species has a laxly-branched corallum 

 with very long and close-set spines. The polyps do not project much beyond the surface 

 of the ccenenchyma, but are more prominent than those of Aphanipathes. 



Pteropathes Jragilis, n. sp. (PI. IV. figs. 1-4 ; PI. XIV. fig. 4). 



Corallum with a rounded basal dilation for attachment. Stem, near the base, under 

 2 mm. in diameter ; above slightly over 2 mm., on account of the greater length of the 

 spines. The specimen is broken into several pieces — total height probably 45 cm. or 

 more. The stem bears a number of distant elongate branches, irregularly arranged, 5 to 

 15 cm. long, simple, or bearing one, rarely two, branchlets. The branches are usually 

 distant and of a diameter only slightly less than that of the stem. They are usually 

 lateral, rarely opposite, and occasionally a branch springs from the posterior surface of the 

 stem. Some of the lower branches form a very wide angle with the stem ; others, parti- 



