THE ECHINODERMS OF PORTO RICO. 
249 
39. Ophionereis reticulata (Say). 
This handsome ophiuran is very abundant in clean sand in shallow water, especially under 
stones, from Bermuda and Florida to Rio Janeiro. It reaches a diameter of 12 nun., the arms about 
7 times as long. Twenty-one specimens, all small, collected at Ensenada Honda (Culebra), Caballo 
Blanco, Puerto Real, and Guanica Bay, and at stations 6079, 6080, and 6088. 
40. Ophiostig'ma isacanthum (Say). 
This small ophiuran (disk 5 to 6 mm., arms 20 to 30 mm.) occurs sparingly from Bermuda to the 
southern West Indies along shore and in water up to 100 fathoms deep. Its color varies from white 
to brown, more or less variegated, but is usually very light. The arms are usually 5 but sometimes 6 in 
number; the latter specimens may be young. There are 4 small specimens, all from station 6079. The 
smallest has 6 arms and a very small disk. 
41. Ophiacantha bidentata (Retzius.) 
A medium-sized ophiuran, light brown in color, previously known from the North Atlantic. 
A single small specimen from station 6070 seems to belong to this species. 
42. Ophiacantha ophiactoides, nov. sp. (PL 15, figs. 5 to 8.) 
Arms 6, rather short and thick. Disk hexagonal, about 2 mm. in diameter; arms about 8 mm. 
long; .'. R=4<7. Arms about one-half millimeter wide at base. Disk covered with rather coarse scales 
and bearing a number of small, thorny spinules. Radial shields widely separated and only exposed 
at the tips. Upper-arm plates broadly oval, becoming triangular at the tip of arm, rounded in front 
and sharply pointed behind, completely separated by the side-arm plates. Arm-spines 4 ( figs. 7, 8), 
approximately equal and smooth to the eye, but very spiny under a lens, about equaling a joint. 
Under-arm plates somewhat pentagonal, with rounded corners and an angle directed inward. Tentacle 
scale 1, small. Oral shields very large, rounded without, bluntly pointed within, much wider than 
long. Adoral plates long and narrow, wider at the outer end, not meeting without or within. Oral 
papillae not very large, smooth, 3 on each side and 2 at tip of jaw, and a large oral tentacle scale at 
distal end. Genital slits 2 in each interbrachial space. Color, very pale yellowish-green, the arms 
banded with brown, each band about twice as wide as the intervening space. 
One specimen of this curious little ophiuran was taken at station 6076, on coral sand, in 10 
fathoms, at Gallardo Bank, Porto Rico. It does not seem to be very nearly allied to any previously 
known species, but as it is probably immature, it may prove to be the young of some other form. It 
resembles Ophiactis krebsii superficially, especially on the upper surface, and for that reason I have 
called it ophiactoides. 
43. Ophialcaea glabra, nov. sp. (PI. 15, figs. 1 to 4.) 
Arms 5, rather stout. Disk pentagonal, about 12 mm. in diameter. Arms all broken, 2\ mm. 
wide at base. Disk covered with a thick, rather rough skin, which covers a very fine scaling visible 
only when the specimen is very dry. Radial shields wholly covered, but showing indistinctly through 
the skin, large and separated. Upper-arm plates broadly in contact, much wider than long, somewhat 
narrowed proximally, with rather acute outer angles; on one arm they are divided into 2 by an 
irregular line, perhaps due to an accident. Arm-spines 8 (figs. 3, 4), glassy, flattened, blunt, and 
slightly rough; approximately equal, about half as long again as the joint. Under-arm plates almost 
square, slightly convex distally. Tentacle scales 2, very large, about equaling the under-arm plate. 
Oral shield large, elliptical, much broader than long, touching the first side-arm plate. Adoral plates 
long and narrow, touching within, wider and widely separated without. Oral papillae 6 or 7 in a 
single row, with 1 median tooth papilla; all long, acute, and rather narrow. On the face of the 
jaw is a little cluster of very small, round knobs. Genital slits prominent, 2 in each interbrachial 
space. Color, uniform dark brown above; on the interbrachial spaces below are a few scattered spots 
and blotches of yellowish white; under side of arm and mouth parts whitish. 
There is a single specimen of this curious species from Playa de Ponce. Although in the 
arrangement of the oral papillae it is a typical Ophiacantha, it differs sharply from that genus in the 
arrangement of the upper-arm plates, the arm-spines, and the covering of the disk. Verrill has recently 
divided the genus into a dozen sections (Trans. Conn. Acad., vol. x, pt. 2, Oct., 1899) and of these 
