60 ON THE ECHINODERMATA OF THE 



OPUIOGLYPHA SAKSII, LutJeen, sp. Plate IV, Figs. 3, 4. 



Ophioglypha Sarsii, Liitken, Videnskabeligo Meddelelser fra den Naturhistoriske Forening i Kjobenhavn, 

 November 1854. 



An Ophioglyplia with mouth-shields shield-shaped, longer than broad ; length less 

 than, or only equal to, their distance from the margin of the disk. Papillae of the 

 disk-incision about fifteen and rather broad. Under arm-plates widely separate, of a 

 very broad, short triangle-shape. Two tentacle-scales. No infrabrachial indentations. 

 Spines rather long, equal in length to the side arm-plates. 



This is the most northerly Echinoderm brought home by the Expedition, a fine 

 specimen, with a disk-diameter of 26 millims., having been taken by Capt. Feilden at 

 the winter-quarters of H.M.S. 'Alert,' in N. lat. 82 27', in 10 fathoms. Other 

 examples of this species were obtained at Discovery Bay in 25 fathoms, and among 

 them one which is provided with remarkably long arm-spines, being in relative 

 proportion fully twice the length of the spines generally occurring in Ophioglypha 

 Sarsii. In this individual the three spines of the sixth joint measure respectively 

 2'45 millims., 2-25 millims., 1'4 millim., the under arm-plate being - 7 millim. long, 

 the arm-joint 1 millim., and the disk-diameter 15 millims. The remaining features of 

 the specimen agree too closely with the characters of Ophioglypha Sarsii (Liitken, sp.), 

 in our opinion, to warrant its removal from that species, even as a provisional variety. 

 Specimens were also found oft' Hayes Point. 



In some cases great irregularity is exhibited in the mouth-papillae, one abnormal 

 example being particularly worthy of notice. In the Ophioglyphce the innermost 

 mouth-papilla generally stands immediately under the teeth, and might be easily 

 mistaken for a tooth, being, in fact, affixed to the tooth-plate and not to the lateral 

 plates. In 0. Sarsii, as well as in other members of the genus, two additional 

 papillae are generally associated with it, one on either hand, and are in like manner 

 borne by the ossicle upon which the teeth are placed. 



In consequence of this arrangement it has long seemed probable to us that these 

 subdental papillae should be regarded as tooth-papillae (of which they are in truth the 

 homologues) rather than as mouth-papillae so-called, along with which they are 

 commonly counted. One of the specimens taken in Discovery Bay throws considerable 

 light upon this question. 



In this individual the dental armature consists of four teeth regularly superposed, 

 following upon which, and occupying the same breadth as a tooth, are three ossicles 

 which fit to one another, wedgewise, with sloping sides. Then come two which fit 

 together and correspond in their shape with the irregularities of the upper and under 

 tier, which latter consists of from three to five compact, close-fitting papillae ; and these 

 again are succeeded by three or four (in some rays five) moderately long, round-tipped, 

 smaller papillae, the whole forming a compact mass suggestive, in the highest degree, 

 of ordinary tooth-papillae, such as occur, for instance, in Ophiothrix ; and yet in every 

 detail, even to measurements, the specimen conforms to the diagnosis of Ophioglypha 

 Sarsii. This individual has a disk-diameter of 22 millimetres. 



Bearing in mind the tendency towards vertical reduplication of the mouth- 

 papillae in some genera, this cannot fail to be regarded as suggestive of the manner in 



