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



oxamincd tlicre arc two pores in the oral plate of the anal intorradius, and there are no 

 others in any of tlio anfimbnlaoral plates which lie between it and the edges of the radials. 

 The remaining oral plates, however, are not invariably pierced by the water-pores, as 

 pointed out in Chapter VI. {ante, p. 95). 



Tlic five ambulacra which radiate outwards from thu inoutli are protected as soon as 

 llicy Iiave passed through the angles of the oral pyramid by a very complete armour of 

 calcareous plates (PI. VI. fig. 8). This seems, as in most recent Crinoid.s, to be less 

 coniph'tcly differentiated on tlie arms than on the j)innulc;s. In the wider, basal and 

 middle portions of tlie pinnules which contain the fusiform genital glands, every 

 jiinnule-joint supports two or three quadrate side plates upon each side (PI. Vc. 

 figs. 9, 10, sp). Upon each of the side plates rests one of the covering plates (cp), which 

 overlap (me another alternately from opposite sides. There are no large side plates, 

 however, in the narrow, proximal portion of the jiinnule before the genital cord swells 

 out into the fusiform genital gland ; ])ut the covering plates are separated from 'the 

 pinnule-joints by a number of small irregular plates which belong to the anambulacrai 

 system (PI. Vc. fig. 10). Towards the distal end of the pinnule, on the other hand, the 

 covering plates Test directly upon the edges of the pinnule-joints (PI. Vc. figs. 8, 9 ; 

 PI. VI. fig. (')), as is the case throughout the entire length of the ambulacrum in 

 Bathicrinus and Rhizocrinm (PI. Vfl. fig. 7; PI. VIII. figs. 4, 5; PI. IX. figs. 2, 4). 

 They are of a slightly oval shape, and may be as much as 0"6 mm. in diameter. 



The genital glands are long and fusiform, and give a swollen appearance to the lower 

 portions of the pinnules (PI. VI. fig. l). This lasts for about six or seven of the 

 elongated joints, after which the pinnules taper away slowly to their extremities, while 

 the glands themselves are continued onwards for some little distance as delicate cords 

 ^^llil■ll (ifYen have a somewhat imdulating course, and gradually diminish in size until 

 they are no longer traceal)le (PI. Vc. fig. 8, i). The axial <xird of the .skeleton (a) is also 

 thrown more or less into curves. The specimen obtained was a male, and the testes have 

 lost all trace of histological structure, as seems to be not unfrequcntly the case with these 

 glands in other species of Crinoids. They fill up the cavity of the pinnxde almost entirely 

 (I'l. \c. fig. 7, t). A reduced ca>liac canal (of) with its ciliated cups [cic) being visible 

 below the gland in transverse section; while a small subtentacular canal {stc) intervenes 

 between it and the water-vessel. Tlie amliulacral nerve and blood-vessel, however, could 

 not be detected, though there can of course be no possible doubt as to their presence. 



In one of the fragments ' which was obtained, the interior of the oral pp'amid is 

 ex]>osed (PI. VI. fig. 5). There is a ring of tentacles around the mouth, and, so far as can 

 be judged from the condition of the specimen, there .seem to be four of these on either 

 side of the strong lui'dinn keel of eaeb oral plate, so that there would be forty in flU. 



' Mr. Blnek did not st'o the original of this figiuv, luit siiuidy copied the woodcut, drawn in fho first instance by Mr. 

 Wild, which iipiH'arod in thv Joxim. Linn. Soc. Land. Zool.) vol. xiii. p. 04, and subsequently in The Atlantic vol. ii. p. 96. 



