MUSEUM OF COMPARATIVE ZOOLOGY. 331 



of the slit ; large, round, scale-like. Teetli four, flat, a little swelled, with a 

 convex cutting edge, which in the lowest one (and to a less degree in those 

 above) has a little lobe at its inner point. Mouth-shields small, swelled, 

 broad heart-shape ; length to breadth .2 : .3. Side mouth-shields small and 

 narrow, not meeting within ; soldered without to the inner lateral side of 

 the second under arm-plate. Under arm-plates nearly pentagonal, with 

 the angle directed inward, and truncated, making a very short sixth side ; 

 outer side curved ; laterals re-enteringly curved ; inner laterals straight ; 

 length to breadth (5th plate) .3 : .3. Side arm-plates stout, meeting above 

 and nearly below. Upper arm-plates as wide as the arm, broader than long, 

 bounded without by a clean curve, within by a very obtuse angle ; length to 

 breadth (3d plate) .3 : .4. Disk covered above and below with neatly im- 

 bricated scales, which are rather larger near the centre, where there are 

 about 30 to a square mm. Radial shields slender pear-seed shape ; a little 

 bent so ?.s to present a concave side to each other ; separated for nearly or 

 quite their length by a wedge of two or more elongated scales ; length 

 to breadth .8 : .4. No grains or spines on the disk scales, which are 

 quite smooth. Arm-spines smooth, moderately stout, rounded, regularly 

 tapering to a blunt point ; nearly equal ; lengths to that of the under 

 arm-plate (5th joint) .5, .5, .5 : .3. One large, round tentacle scale, which 

 resembles the mouth-papilla. Color, in alcohol, pale brown. 



This species is distinguished from others by its lobed teetli and the entirely 

 naked disk scales. It belongs to the group that have the side mouth-shields 

 joining the under arm-plate. Off Carysfort Reef, 117 fathoms; off Key 

 West, 140 fathoms; off Boca Grande, 125 fathoms; off Tortugas, 13 fathoms. 



Opliiactis loricata Lyjian, sp. now 



Special Marks. — Side mouth-shields with their outer side touching the 

 side arm-plate, and the first and second under arm-plates. Radial shields 

 small. Upper and lower arm-plates long. Six arms. 



Description of a Specimen. — Diameter of disk 2 mm. Length of arm 

 7 mm. Mouth-papillae usually four to each mouth-angle, two on each side 

 mouth- shield, of which the inner is very small and spine-like, but situated 

 at the same level. Sometimes this second minute one is wanting, some- 

 times it is nearly as large as the outer. These variations may be looked 

 for, because these creatures are peculiarly liable to mutilation, so that, of 

 five specimens dredged, only one was perfect and symmetrical. Teeth, 

 four; the upper one more sharp and narrow; the lowest sometimes divided 

 into two papilla?. In the teeth, again, there seems some variation. Mouth- 

 shields small, broad oval, rather swollen. Side mouth-shields stout, long 

 triangular, nearly meeting within ; the inner corner of the outer side (its in 

 just where the first and second under arm-plates touch each other; the 



