MUSEUM OF COMPARATIVE ZOOLOGY. 273 



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

 of disk 13 mm. Width of nrni close to disk 3 mm. Length of aim 95 mm. 

 Four fiat, rounded papillae 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 aide 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 epiite 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 upwards 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 differed in having, with a disk of 9 mm., two, or at 

 most three, arm-spines. The radial shields were as in 0. 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- 

 oms. 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 fath- 

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

 fathoms. Station 203, Martinique, 96 fathoms. Station 205, Martinique, 

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

 cent, 95 fathoms. Station 232, St. Vincent, 88 fathoms. Station 838, Grena- 

 dines, 127 fathoms. Station 241, Grenadines, 163 fathoms. Station 846, 

 Grenada, 154 fathoms. Station 217, Grenada, 170 fathoms. Station 869. 

 Grenada, 159 fathoms. Station 869, St. Vincent, 184 fathoms. Station 872, 

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

 bados, 94 fathoms. Station 278, Barbados, 69 fathoms. Station 881, Barbados, 

 288 fathoms. Station 286, Barbados, 13-40 fathoms. Btation290, Barbados, 

 73 fathoms. Station 291, Barbados, 200 fathoms. Station 896, 



