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



seem to show sufficient differences to fairly entitle them to generic rank ; Muricea is 

 therefore taken here as a genus in the sense of Verrill's subgenus, which is characterised 

 as having species " in which the verrucae are bilabiate, or have a prolonged lower lip. The 

 spindles of the coenenchyma and verrucse similar, and usually stout, but sometimes slender 

 and pointed." To which may be added, that the tentacles in repose are quite withdrawn 

 into the calyx ; the basal portions of the tentacles, however, are armed with needle or 

 spindle-shaped spicules, which form an octoradiate incomplete operculum, which lies over 

 the infolded tentacular portions of the polyps. The largest number of the described 

 species are found on the west coast of America, a few are met with in the Atlantic. 

 The Challenger collection contains but a single species, which appears to be new. 



Mxiricea bicolor, n. sp. (PI. XXIII. fig. 11 ; PI. XXV. fig. 8). 



1 Eunieea humilis, Milne-Edwards, Hist. Nat. des Coralliaires, vol. i. p. 1 49. 



The stem in this species forms a short, upright axis, arising from a flat base ; 

 branches are given off in a triradiate manner ; these are sometimes short, simple, 

 terminating in knob-like masses, and are given off at right angles ; sometimes rather 

 large, and nearly of the strength of the main stem, these are furnished with smaller 

 branches in the same manner as in the principal axis ; these last have also again small 

 lateral twigs. The larger branches arise at obtuse angles, but soon bend upwards and 

 run parallel to the main stem. The principal stem is 80 mm. high, and 3 mm. in 

 diameter at its base. The larger branches are from 40 to 60 mm. long, with a basal 

 thickness of 2 mm. The terminal branches reach to a length of from 15 to 24 mm., 

 with a thickness of 2 mm. at their base, increasing to 2"5 mm. at the extremities. The 

 branches are about 2 mm. apart. The ccenenchyma is thick and rough on the surface. 

 On a section being made, two layers of spicules are seen, the outer layer, 0'7 mm. thick, 

 with rough spindles unilaterally spined, of a yellowish-white colour ; the inner layer of 

 0'3 mm. thickness, the spicules of a violet hue. The polyps are laterally compressed, 

 with oval mouths, whose long diameters are turned to the stem. They are so flattened 

 to the stem that only a small portion of the outer body-wall projects free ; the outer 

 margin of the body is a little protruded, and forms a short lip. The tentacular portions 

 of the polyps are quite retractile, the basal portion of each tentacle is furnished with 

 needle-shaped spicules, which help to form a rudimentary covering over the tentacles. 

 The spicules of the coenenchyma and of the polyps are on the exterior large, one-sided 

 spiny spindles ; the spines present the form of dentate, often branched eminences, which 

 arise in two parallel rows from the spindles, and sometimes, becoming confluent, form 

 spiny combs. In addition to these, there are branched spines from the whole spindle. 

 Sometimes the spindle is short, while the spiny comb-like portions are strongly developed. 

 In other cases one end of a spindle will be expanded into a series of branched spines and 



