52 



pointed termination to the interior truncated and excavated point, forming two 

 slanting sides for the adhesion of the first arm joint. Each of these are tra- 

 versed by a perforated ridge running in a slanting direction from the interior to 

 the exterior point. 



The ARMS. -The ten arms proceeding from the five scapulae, (two from each) 

 are each formed of five joints nearly of an horse-shoe figure, sending off from 

 their alternate sides the tentacula. The superior surface of the first arm joint 

 (PL. ii. fig. 4.) and the inferior of the second, are subconcave, perforated in 

 the centre, smooth, with fine radiating ridges at the circumference, and want 

 the transverse subtriangular ridge which exists in the following arm and finger 

 joints. In these it traverses the superior surfaces (PL. n. fig. 1. to 3.) in an 

 angle from near the place where the tentaculum sets off to the opposite exte- 

 rior circumference, and at the inferior surface in an opposite direction to the 

 former. On the inside the joint is excavated in the centre in a sharp angle, 

 it is thicker on the side which sends off the tentacula, being there cut in an ob- 

 liquely transverse section, of which the lower portion shows a ridge, the mark of 

 articulation, whilst the upper forms a slender lamina. The projecting point on 

 the other side is slantingly cutoff to permit room for the action of the tentacu- 

 lum from the joints below it. There are also several irregular rugaj on the ar- 

 ticulating surfaces, serving as points of adhesion to the muscular integument. 



The upper or sixth joint of the arm (PL. n. fig. 11. to 14.) resembles in 

 figure the scapula; this, and those other joints bearing an analogy to it, I have 

 distinguished by the name of cuneiform joints, from their upper surface posses- 

 sing two opposite slopes, and, like a wedge, interrupting the further continu- 

 ing of a series of joints, and rendering it dichotomous. 



The cuneiform joints never send off a tentaculum, and to obviate the 

 interruption or vacuity thus occasioned in the beautiful net-like apparatus 

 displayed when the hands and fingers with their tentacula are expanded, the 

 number of joints below the cuneiform one generally varies in the hands; thus 

 affording an opportunity for the insinuation of the tentaculum arising from 

 the neighbouring hand, into the vacant place if required. 



The HAND and FINGERS. (Pi,, i.) These are twenty in number, two pro- 

 ceeding from the cuneiform joint of each arm. Each series proceeds through 

 about eight or nine joints, and then by means of another cuneiform joint gives 



