THE ECHHSTODERMS OF PORTO RICO. 
239 
OPHXUROIDEA. 
BRITTLE-STARS, SAND-STARS, SERPENT-STARS, ETC. 
The brittle-stars make up by far the largest and most interesting part of the 
collection of echinoderms made by the Fish Hawk. There are about 550 specimens, 
representing 19 species, of which no less than 7 seem to be new to science. In spite 
of the fact that the ophiurans of the West Indies have been long and carefully 
studied by some of the best systematists in the world, so great is their number and 
so extraordinary their variety that almost every collection of any size adds something 
new to the list. This is especially true when collecting with a tangle, for a dredge 
or trawl is of little use on a bottom covered with coral, while a tangle quickly gathers 
up any objects as rough as the ordinary brittle-star. Of course, on sandy or muddy 
bottoms, where the ophiurans are buried, a dredge or trawl is better. Half of the 
specially interesting forms collected by the Fish Hawk were taken with the tangle; 
all but one or two of the remainder were taken Avit.h the dredge or 7-foot, trawl. 
Aside from those Avhich are new, there are several species of very great interest on 
account of the considerable extension of their range or the discovery of their pres- 
ence in shallow water when previously known only from considerable depths. There 
are 17 species which were collected along shore, the remaining 31 having been taken 
at depths of from 1 to 231 fathoms. In the study of this collection Professor Yerrill’s 
recent papers on West Indian Ophiurans (Trans. Conn. Acad., vol. x, pt. 2) have 
been of the greatest value, and his classification and nomenclature have been adopted 
in the following list except in one or two instances. 
The following very artificial key to the brittle-stars of Porto Rico (on pp. 240- 
211) is rendered more or less technical on account of the large number of species and 
the close relationship between many of them. Consequently it has been necessary to 
make use of certain terms that may not be readily understood by one not familiar 
with the group. These terms are herewith briefly defined in order to make the key 
thoroughly intelligible: 
Adoral plates. — A pair of small plates at the base of the jaws, proximally close to the oral shields. 
Arm-comb. — A series of very small teeth-like projections or papillae bordering the plates of the disk at 
the base of the arm in the genus Ophioglypha. 
Arm-spines. — The spines borne on the side of the arms; the number of arm-spines is the number in a 
single vertical row. 
Disk. — The body, as distinguished from the arms, especially the upper side of the body. 
Distal. — Away from the mouth; toward the tip of the arm. 
Jaws. — The five triangular bodies which surround the mouth, each one made up of several plates and 
bearing the oral papillae and tooth papillae. 
Oral papillae. — The teeth-like projections on the sides of the jaws. 
Oral shields. — The large plates lying one in each interradius between the bases of the arms, on the 
under side, just outside the bases of the jaws. 
Proximal. — Toward the mouth or base of the arms. 
Radial shields. — Large plates on the surface of the disk, arranged in pairs at the base of the arms; they 
may be very large, or small, or entirely concealed; the two shields of a pair may lie close 
together or widely separated. 
Tentacle pores. — Openings on under side of arm, through which tentacles project in the living animal. 
Tentacle scales. — Small scales, just outside the under-arm plates and close beside the tentacle pores. 
Tooth, papilla; . — The teeth-like projections at apex of jaw. 
Under-arm plates. — The longitudinal row of plates covering the lower surface of the arms. 
Upper-arm plates. — The longitudinal roAV of plates covering the upper surface of the arms; usually they 
form a single continuous series, but sometimes they are widely separated from each other, 
and occasionally there are additional rows composed of supplementary plates on each side. 
