AGASSIZIA EXCENTEICA. 71 
Agassizia excentrica A. Ag. 
Florida, Cuba, Lesser Antilles. 86-391 fatbums. 
For list of Stations, see Bull. M. C. Z., V., No. 9, p. 193, 1878 ; VIII., No. 2, p. 83, 1880. 
PI XXV. 
When alive the test is covered with spines of a dehcate ^oinkish gray color, 
darkest at the base. The ambulacral areas are covered with slender, long- 
stemmed, small-headed pedicellarite, articidated at the base, while in the 
interambulacral system the miliaries carry slender, straight, or slightly 
curved club-shaped spines, scarcely stouter than the stems of the pedicel- 
larire. The fascioles are still more thickly crowded with similar minute 
pedicellaria3 and club-shaped miliary spines, but somewhat shorter, and 
closely dotted with large pigment spots. 
The actinostome of the genus is marked for the irregular arrangement of 
the buccal plates. The anal plates are few in number, often less than eight, 
comparatively large, and form in the 3'oung stages a regular anal pyramid, 
as characteristic as that figured by Gray, Loven, and myself in Pala^ostoma. 
A few of the tentacles of the odd anterior ambulacrum, near the apical 
system, are fimbriated like those surrounding tlie buccal system ; those 
immediately following towards the ambitus are simple, with a slight sucking 
disk like the tentacles of the anterior rows of pores of the lateral petaloid 
ambulacra. Within the petaloid area the tentacles of the posterior rows are 
broader, compressed, irregularly lobed at the extremity; the tentacles beyond 
become, as in the anterior rows, simple towards the ambitus, and remain 
so till they join the large fimbriated tentacles surrounding the buccal 
system. The presence of large fimbriated tentacles near the apical system 
in the odd ambulacral petal shows that Agassizia is itself an embryonic 
genus. Other features of the same character are the general globular form, 
and the rudimentary structure of the lateral anterior ambulacra ; the an- 
terior rows of pores of the posterior lateral ambulacra appear only after 
the posterior rows are well developed. 
In a specimen measuring 3 mm. in length, -the first ambulacral tentacles to 
appear are those surrounding the actinostome, which were nine in number 
and already fimbriated. In the denuded test of a specimen of about the 
same size, no trace of the subdivision of the test into coronal plates could 
be detected ; it consisted entirely of a close network of fine granulation. 
