PHORMOSOMA PANAMENSE. 101 



Station 3432, off Altata, 1421 fathoms. Lat. 24° 22' 30" N. ; Long. 

 109° 3' 20" W. Butt, temp. 37 .8. Br. m. blk. sp. 



Bathymetrical range, 995-1421 fathoms. Temperature range, 37°.8-36°. 



Phormosoma panamense A. Ag. 



Phormosoma panamense A. Ag., Bull. M. C. Z. 1898, XXXII. No. 5, p. 77. 



Only three specimens of this species were collected, all in poor condition, 

 measuring from 130 to about 1G0 mm. in diameter, having lost all but a few 

 broken shafts of their spines. It. as well as its ally Ph. ten/ie, is noted for the 

 great elongation of the abactinal plates of the test, much as in Asthenosoma, 

 though the}' are not bordered by the bare spaces which leave a central 

 limestone ridge in the interambulacral plates, so characteristic of As- 

 thenosoma. The primary tubercles of the interambulacral plates are 

 arranged in three or four vertical rows; the remainder of the plate is 

 dotted with deeply sunken miliaries. 



The apical system of a specimen 130 mm. in diameter is 25 mm. in 

 diameter. The arrangement of the ambulacral pores recalls that of 

 Ph. luculentum} 



Dr. Mortensen is distressed because 1 have as yet (1903) given no 

 figures, nor complete information, regarding Ph. panamense, a species which 

 is only mentioned in the Preliminary Report on the Echini of the '• Alba- 

 tross " Expedition of 1891," and he finds it impossible to find a place for 

 this species among his genera ; he limits the genus Phormosoma to species 

 with skin-covered spines. I have stated that I thought this character 

 of no great systematic importance. 3 Dr. Mortensen 4 is of a contrary 

 opinion. 



The color of the fragments of the test which came up in the trawl were 

 light pinkish brown. At the ambitus the width of the ambulacra is greater 

 than that of the interambulacra. Comparing a specimen of this species 

 of 130 mm. in diameter with one of Ph. hispidum 140 mm. in diameter, we 

 find the interambulacral plates of the actinal side of the former quite 

 thickly covered with miliaries, while in the latter the miliaries are quite 

 scattered. There is also a line of six and eight primary tubercles with 



1 "Challenger" Echinoidea, PI. IX", fig. 2. 8 "Challenger" Echinoidea, p. 101. 



2 Bull. M. C. Z. 1898, XXXII, p. 77. 4 Mortensen, loc. cit. p. 48. 



