328 ENCOPE EMAEGINATA. 



In older specimens, where the posterior interambulacral lunule has just 

 forced its way to the dorsal portion of the test (PL XIJ. f. i;). the abactinal 

 part of the ambulacra is petaloid, the last two pairs of pores alone are not 

 connected by furrows, and are pierced between two adjoining ambulacra] 

 plates, while the other pairs, fourteen in number, are joined by furrows. 

 These fourteen plates correspond to four interambulacral plates, showing a 

 different rate of growth between the plates of the interambulacral and am- 

 bulacra! series. The sutures between the various ambulacral plates have 

 become obliterated, there are a large number of tubercles on each plate, and 

 the genera] aspect of the upper surface begins to resemble more closely that 

 of the adult. The madreporic body is well developed, no genital openings 

 yet. The pores on the lower surface are particularly numerous round the 

 actinostome, forming ten points, somewhat like phyllodes (PI. XII. f. is). 

 baving their origin on each side of the rotules. In a somewhat more ad- 

 vanced stage the lines of pores are connected ai their base, and fork at a 

 short distance from the mouth (PI XII. f. :i). The interambulacral platen 

 on the lower surface are covered by larger tubercles than the others. 

 making five narrow zones, in contrast with the ambulacra! region, where the 

 tubercles are very minute. 



The outline of the young stages of Encope ( PL XII. f. 20-24) before the 

 closing of the lunules. while they are still mere indentations, recalls strongly 

 the post-pliocene form Monophora, and some of the other species of Encope 

 found on the west coast of Florida and the (lull' of California. E Michelini 

 and E. grandis. 



Dr. Liitken, in his discussion of Encope emarginata, has given figures of 

 young Encope after the appearance of the posterior interambulacral lunule. 



The madreporic body is large, quite markedly stellil'onn. the ocular plates 

 often rising as sharp ends from its sales, the genital openings are large and 

 placed at a considerable distance from the centre of the madreporic hody 

 within the median interambulacral space. The posterior pair of ambulacral 

 petals are longer than the others, the odd petal somewhat shorter, and the 

 anterior pair of ambulacra intermediate in length. The poriferous zone has 

 about the same width in all the petals, hut the median ambulacra! space of 

 the posterior ambulacra is quite narrow compared to the others, the porif- 

 erous zone being broader than this median space in the posterior ambulacra. 

 The posterior lunule extends to within one quarter the distance of the 

 mouth from the edge of the test, the anus is placed quite near the mouth 



