EASTERN TROPICAL PACIFIC ASTEROIDEA. 107 
how many notable forms are recent discoveries, and emphasizes the fact that we 
are as yet far from realizing the entire content of the family. This idea is still 
further emphasized by the present collection, for while there are only eight disks 
and some scattered arms from but five stations, no fewer than five species are 
represented and four of these are new to science.' The one previously described 
species moreover has hitherto been known only from the eastern tropical Atlantic, 
where it was taken by the CHALLENGER! Three of the five species were taken 
at a single station. These facts all go to show how very incomplete our knowl- 
edge of this remarkable deep-sea family still is. Of very few species has sufficient 
material been secured to permit real knowledge of the specific characters, and 
there is not a single form of which the growth-changes and the limits of indi- 
vidual diversity are known. Under such circumstances the addition of new 
species based on single and more or less fragmentary specimens is not very 
desirable, but on the other hand material so rare and so difficult to secure must 
not be ignored. The following notes may be of service in elucidating generic 
and specific limits within the family. 
Brisingella monacantha,? sp. nov. 
Plate 5, fig. 3, 4. 
Disk and number of rays unknown. Rays about 200 mm. long, 4 mm. 
wide at base, 5.5 mm. wide at middle of genital area and 2.75 mm. wide one 
hundred millimeters from base. Genital area begins 10 mm. from proximal 
end of ray and extends about 25 mm.; it is covered by delicate naked gray skin 
and is crossed by eleven or twelve calcareous ridges (“‘primary costae”’ of Fisher) ; 
there are three or four additional costae distal to the swollen area and indications 
of four or five more proximal to it; there are two incomplete or secondary costae 
on each ray; otherwise there is no calcareous material on dorsal side of rays. 
Adambulacral plates about 2 mm. long on proximal half of ray, somewhat 
shorter distally; width at proximal end about half length, distinctly less at 
middle and slightly more at distal end where there is a marked projection or 
peak on the inner corner; at the base of this peak on the actinal surface of plate 
but close to the adambulacral margin is a distinet spine-bearing tubercle; on 
proximal part of arm, there is a fairly close approximation between costae and 
1 Tt is interesting to note that all of the specimens were taken in water more than 2,200 fms. deep 
and at a temperature lower than 36° F. 
2 monacanthus = having a single thorn or spine, in reference to the armature of the adambulacral 
plates. 
