MUSEUM OF COMPARATIVE ZOOLOGY. 273 



Description of an Individual (21° 23' 19" N., 82° 54' 42" W.). — Diameter 

 of cli.sk 13 lum. "Width of arm close to disk 3 mm. LenL;th of arm 95 mm. 

 Four flat, rounded papilla; with rough cutting edges on each side of the mouth- 

 angles; and five or six teeth of similar form, but with nearly smooth edges. 

 Mouth-shields showing indistinctly under the skin as transverse oval figures. 

 On boiling the skin of the arm in potash there are found under arm-plates of 

 a shield-shape, with a strong central notch and two angles on the outer side 

 and a peak within; while the side arm-plates are seen as ridges nearly meeting 

 below, where they are thickest, and have a notch in their outer side through 

 which passes the tentacle. Only a trace of upper plates in form of little 

 crusts of lime. Disk five-sided with re-entering curves; covered by a naked, 

 loose, wrinkled skin, under which is found a continuous marginal line of 

 small plates, which runs quite round the entire edge. Attached by their 

 outer ends to this line of plates are small, short, club-shaped radial shields, 

 which have no such cluster of small scales as are often found in the genus. 

 Four or five slender, somewhat flattened, blunt, slightly rough arm-spines, 

 about as long as a joint. No tentacle-scales. Color in alcohol, disk gray; 

 arms straw. 



Usually this genus has low side arm-plates, and a high arch of separate 

 pieces which represent the upper arm-plates. The latter are nearly wanting 

 in 0. tumida, while the side arm-plates run somewhat farther upward.s than 

 common. 



Two other lots from Stations 319, 32° 25' N., 77° 42' 30" W., 262 fathoms, 

 and 320, 32° 33' 15" N., 77° 30' 10" W., 257 fathoms, may be the young of this 

 species. The specimens diifered in having, with a disk of 9 mm., two, or at 

 most three, arm-spines. The radial shields were as in O. tumida, but there 

 was no well-marked marginal line of plates. There were, however, microscopic 

 crust-like scales under the disk skin, which may also be detected in 0. tumida. 

 The specimens were fertile and were viviparous. 



Station 132, Santa Cruz, 115 fathoms. Station 139, Santa Cruz, 218 fath- 

 om.s. Station 146, St. Kitts, 245 fathoms. Station 147, St. Kitts, 250 fathoms. 

 Station 148, St. Kitts, 208 fathoms. Station 155, Montserrat, 88 fathoms. 

 Station 156, Montserrat, 88 fathoms. Station 157, Montserrat, 120 fathoms. 

 Station 158, Montserrat, 148 fathoms. Station 165, Guadeloupe, 277 fixth- 

 oms. Station 172, Guadeloupe, 62-180 fathoms. Station 177, Dominica, 118 

 fathoms. Station 203, Martini(ine, 96 fathoms. Station 205, ]\Iartini(|ue, 

 334 fathoms. Station 220, St. Lucia, 116 fathoms. Station 231, St. Vin- 

 cent, 95 fathoms. Station 232, St. Vincent, 88 fathoms. Station 238, Grena- 

 dines, 127 fathoms. Station 241, Grenadines, 163 fathoms. Station 246, 

 Grenada, 154 fathom.s. Station 247, Grenada, 170 fathoms. Staticm 259. 

 Grenada, 159 fathoms. Station 269, St. Vincent, 124 fathoms. Station 272, 

 Barbados, 76 fathoms. Station 273, Barbados, 103 fathoms. Station 276, Bar- 

 bado.s, 94 fathoms. Station 278, Barbados, 69 fathoms. Station 281, Barbados, 

 288 fathoms. Station 285, Barbados, 13-40 fathoms. Station 290, Barbados, 

 73 fathoms. Station 291, Barbados, 200 fatlioms. Station 296, Barbados, 



