THE EOHINODERMS OF PORTO RICO. 
253 
3. Asthenosoma hystrix (W. Thomson). 
As this urchin occurs only in deep water, it is not likely to be met with by the ordinary collector. 
It reaches a large size (140 mm. in diameter), hut the test is always soft and flexible. The spines are 
short but very sharp, and scattered rather sparsely over the test. The feet are in three vertical rows 
in each poriferous zone in the adult. 
There are two large specimens of this very curious flexible urchin, both' as flat as can be. They 
measure 135 and 140 mm. in diameter, but are only 7 mm. thick. The abactinal surface is purple 
and the actinal very pale yellow. These specimens were collected at station 6070, and from the 
same place there are two very small flexible urchins, 10 mm. in diameter, which I refer with some 
hesitation to this species. Their coloration is precisely like that of the large ones, but the feet are in 
only a single row in each poriferous zone instead of in three rows, as in the adult. 
4. Diadema setosum (Tray. 
One of the most characteristic urchins of the Tropics; of world-wide distribution from Cuba east- 
ward to the Fiji Islands. Almost black, but the spines are often banded with white in the young. 
The adults are sometimes 100 min. in diameter, with spines 300 or 400 mm. long. Very common 
about coral reefs. 
The Fish Hawk collection contains twenty specimens of this species, varying from 17 to 75 mm. 
in diameter, and collected at Ponce, Mayaguez, and Arroyo. The smallest (those less than 40 mm. 
in diameter) usually have the spines banded light and dark, whitish or yellowish, alternating with 
purplish or brownish. One large specimen has all the spines on the actinal surface white. A large 
specimen from Ponce differs markedly from all the others in that a number of the spines, especially 
on the actinal surface, have prominent swollen “ rings,” 6 to 10 mm. wide and 2 to 3 mm. in diameter, 
about 25 mm. from the base. As all the spines are broken, I am not sure whether this swelling is 
always at the tip of the spine or not, but it appears as though it was. The spines are horizontally 
ringed, but these swellings are longitudinally ridged. 
5. Echinometra subangularis (Leske). 
This species is often called the “rock-boring” urchin, because of its habit of living in cavities in the 
reefs and ledges in shallow water. In size it is rather small, not often 50 mm. long, the spines about 
20 mm. It varies greatly in form and proportions, but especially in color. All stages from very pale 
reddish brown to nearly black are common, while the spines are often green with more or less violet. 
It is found from Bermuda to Rio Janeiro. The collection contains 105 examples, exhibiting a most 
extraordinary range in color and shape. Indeed, the extremes are so different one might easily believe 
there are at least two distinct species in the series. The more common form was collected at Ponce, 
Arroyo, Boqueron Bay, Fajardo, San Juan, and Aguadilla. The largest measures 42 mm. long by 38 
wide by 22 high. The spines are slender, 20 mm. long, and less than 2 mm. in diameter. The color 
varies from bright light green with violet-tipped spines to very light reddish brown and thence through 
varying shades of red-brown to almost black. The other form was collected at Ensenada Honda and 
on the light-house reef at Playa de Ponce. The difference in size is not notable, 1 >ut the test is somewhat 
more flattened. The spines, however, are very different. They measure from 15 to 20 mm. in length 
and from 2 to 3J mm. in diameter. They are much stouter, therefore, and are also somewhat flattened 
and abruptly pointed. Their color varies from pale, dull pink, through reddish brown to dark green, 
the spines having violet tips; in some more than half the spine is violet. 
6. Echinometra viridis A. Agassiz. 
This species closely resembles the preceding in size, shape, color, and habits, and seems to be 
.distinguished only by the bare apical system. It is recorded from Florida, Cuba, and Haiti. Two 
specimens from the reefs at Playa de Ponce seem to be referable to this species. They are of about 
average size and color. The test is brownish; spines light green, almost yellow at base, violet tipped. 
There are no spines within the anal area, and only about 12 to 15 in the whole abactinal system. 
7. Toxopneustes variegatus (Lamarck). 
The common sea-urchin of the tropical western Atlantic, abundant from Bermuda and North 
Carolina to Rio Janeiro. It varies greatly in color from rich violet (Bermuda) to bright green and 
