338 ECHINOLAMPAS DEPRESSA. 



In specimens twice the .size of the above the test is less elliptical, more 

 flattened, and the first trace of a rudimentary rosette appears as a short 

 row of double pores extending from the apex (PI. XVI f. /;), consisting 

 of from eighl to nine pairs, only in one of the poriferous zones of each of the 

 lateral pairs of ambulacra — in the anterior zone of the posterior pair and the 

 posterior zone of the anterior pair of ambulacra — the old ambulacrum re- 

 mains simple. In specimens measuring about 13 mm this rudimentary one- 

 sided rosette has increased in length (PI. XVI f. ?), and traces of the 

 second row of double pores are seen in the simple zones near the apex. 

 In specimens measuring an inch {PI. XVI. /'. .'/(.these rows have grown to 

 be half as long as the arc of the rosette first formed ; the same structure has 

 also extended to the abactinal part of the odd ambulacrum, and the furrow 

 connecting the pores of the petaloid part of the ambulacra (PI. XVI. f. :.') 

 is as well defined as in any old specimen of Echinolampas. The regular 

 elliptical outline so characteristic of the young specimens when seen from 

 above (PI. XVI f. /). and the high globular profile, are gradually changed 

 to a more circular and flattened test, passing through a more or less pen- 

 tagonal outline ( PI. X VI. /'. 8 — 10), and at last with the gradually increasing 

 projection of the posterior extremity the test assumes an ovoid outline ( /'/. 

 XVI. f. 17- 19). While these changes are going on, the miliary tubercles in- 

 crease rapidly in number,* forming clusters of small tubercles, embossing the 

 plates of both areas. This is quite a prominent feature in one of the stages 

 (PL XVI. f. 8- /"). With increasing age the primary tubercles become more 

 numerous, and finally appear as a nearly homogeneous granulation, with closely 

 packed miliaries between, in specimens of about an inch (PI. XVI. /'. 

 17-10). The anal system is covered by three large triangular plates; 

 carrying a few tubercles (PI. XVI f. .7, /.£), the anus opening near the edge 

 of the system, in a narrow slit covered by very minute plates. The mouth, 

 as the young increase in size, becomes more and more sunken, losing little 

 by little its prominently lobed outline (PI. XVI f. 2\ ami passing from this 

 stage through that of a slightly sunken actinostome. showing no trace whatever 

 of the bourrelets or phyllodes ( /7. XVI. f. 9), to the stage represented in 

 PI. XVI f. 18, 20, when the phyllodes are plainly laid out. and the first 

 trace of the bourrelet appears as accumulations of minute tubercles closely 

 packed together (PI. XVI f. 20) between the phyllodes. The buccal mem- 

 brane is covered with minute plates, the mouth opening in the centre of the 

 membrane (PI. XVI. f. 2, 9), as a diminutive slit. When measuring about 



