MUSEUM OF COMPARATIVE ZOOLOGY. 261 



Echinometra viridis A. Ag., Bull. M. C. Z., No. 2. 



Syn. Echinometra Michclini Lutk. (non. A. AG.,necDES.) Bidrag. 

 " plana A. Ag., Bull. M. C. Z., No. 2. 



As in Echinometra Michelini Des. there is a Hat long-spined variety 

 of Echinometra viridis, distinguished formerly as Echinometra plana, but 

 which the full series now in the Museum collection shows decidedly to hold 

 the same relation to E. viridis which Heliocidaris mexicana AtJCT. holds 

 to E. Michelini. 



Same range as former species, much less common. 



'chinus gracilis A. Ag., nov. sp. 



This species holds an intermediate position between E. Flemingii Ball 

 and E. melo Lam., to both of which it is allied. Like the former, it is sub- 

 ject to great variations in the ratio of the longitudinal and vertical diame- 

 ter of the test. The primary tubercles are larger than those of E. melo, 

 but smaller than those of E. Flemingii. The spines in the proportion they 

 bear to test are similar to those of E. melo, as well as the general pattern 

 of coloration, consisting of bands of green made up of irregularly shaped 

 lozenges running in vertical rows, diminishing in intensity towards acti- 

 nostome, the intermediate spaces forming brilliant white or straw-colored 

 bands. In one of these white bands is placed the poriferous zone, and 

 each primary row of tubercles is placed in a similar band. Thus the test 

 is divided into twenty bands alternately green and white ; the poriferous 

 zones and two principal rows of tubercles being separated by these dark- 

 green lozenges, giving the test a most graceful pattern of coloration. The 

 shape of the genital plates of the abactinal system, which is compact and 

 circular, is a pointed pentagon somewhat as in E. melo, while in Flem- 

 ingii they are heptagonal. The anal system is made up of a large num- 

 ber of small plates. The ten large plates of the buccal membrane are 

 quadrangular with rounded corners, carrying stout pedicellaria) similar to 

 those of E. melo. The position and general arrangement of the tubercles 

 is similar to E. melo ; the large tubercle is placed in the centre of the in- 

 terambulaeral plate, which carries in addition short horizontal rows of 

 two or three minute tubercles, the row near the horizontal suture being 

 the most prominent. In the ambulacral zone the main tubercle has a 

 similar position; the small tubercles are placed close to the median su'ure, 

 and form irregular vertical rows. This species attains a considerable 

 size ; specimens are in our collection measuring 2. GO inches in diameter, 

 and another 2.75 inches in height, exceeding somewhat the transverse 

 diameter. 



From 93 to 200 fathoms. 



