114 IOWA STUDIES IN NATURAL HISTORY 



Tripneustes esculentus Bell, 1879. Proe. Zool. Soc. London, 

 p. 657. 



In the Narrative, Professor Nutting refers often to this well- 

 known "sea-egg", one of the very few sea-urchins which have 

 any economic importance. In some cases, the sea-egg is called 

 Hipponoe and in others, the correct name Tripneustes is used. 

 Complaint is made (p. 188) that I have given no clue to the 

 reason for abandoning Hippotwe, but this is hardly fair since I 

 have given the full reference to Bell's paper where the matter 

 was amply elucidated over forty years ago. It is no innovation 

 of mine, to make use of Tripneustes. Hipponoe is preoccupied 

 and there is no good reason for persisting in its use. 



Professor Nutting calls attention (pp. 80, 188) to two inter- 

 esting color forms of the sea-egg, and both are represented 

 among the eight specimens in the present collection. The two 

 forms seem to be reasonably distinct and further investigation of 

 their differences and the causes thereof is worth while. Ap- 

 parently in the pallid form the development of pigment is inhib- 

 ited, only a little on the triphyllous pedicellariae being visible, 

 while the peristome and gills are brown. In the melanistic form, 

 pigment is markedly developed, especially on the peristome (par- 

 ticularly, close to the teeth), in the pedicellariae, in the tube-feet 

 (except the white tips), in the tips of the branches of the gills 

 and even to some extent in the epidermis of the test. The devel- 

 opment of the pigment is not correlated with size but whether it 

 is correlated with age is as yet unknown. 



The specimens at hand range from 34 mm. in diameter to 132 

 mm. The primary spines on the smallest specimen are notably 

 long (9 mm.), more than one-fourth the test-diameter. As a 

 rule, they are hardly half as much as that. 



Of the eight specimens, seven are from Barbados and one is 

 from English Harbour, Antigua. 



GENOCIDARIS MACULATA 



A. Agassiz, 1869. Bull. M. C. Z., 1, p. 262. 1872, Rev. Ech., pi. 

 VIII, figs. 1-18 (as Temnechimis maculatus). 



Two bare, dead tests, without buccal membrane or periproctal 

 plates, are the only representatives of this little sea-urchin in the 



