EXCOPE MICHELINI. 547 



Encopc Michelini 



! Encope Michelini Agass., 1841, Mon. Scut , p. 58. 

 (Sue Part II. p. 329.) 



PL XII". f. 4; PL XII'. f. 3-4; PI XII' 1 . f. l. 



Yucatan ; Florida. 

 Encope micropora 



! Encopc micropora AGASS., 1841. Mon. Scut. p. 50. 



This is the Pacific representative of Encope emarginata. Although the 

 species of Encope vary to an extraordinary extent on the Atlantic side of 

 the coast of North and South America, we find a much greater uniformity 

 in the general appearance of the species found on the west coast of this 

 continent. 



We find neither in E. grandis, E. californica, or E. micropora, such a range 

 of variation as we have described in E. emarginata, and which has led to the 

 discrimination of so many false species. This species is readily separated 

 from E. emarginata. The test is depressed ; vertex anterior, near the ex- 

 tremity of the odd ambulacrum. The outline is rounded anteriorly, truncated 

 posteriorly ; apical system small ; posterior interambulacral lunule small, 

 round, or elliptical nearer the edge than the apex. The petals are com- 

 paratively longer than in E. emarginata, extending towards the margin, 

 so as to leave room for only small elliptical ambulacral lunules. The inter- 

 poriferous space of the petals is broad, as broad as the poriferous zones ; the 

 pores are more closely crowded than in the corresponding Atlantic species. 

 The actinostome is central ; the anus is placed half-way between the mouth 

 and the interambulacral lunule. 



The interambulacral spaces left between the ambulacral furrows are 

 smaller than those in E. emarginata, owing to the greater spread of the fur- 

 rows towards the ambulacral lunules. On examining the interior we find 

 very striking differences between E. emarginata and this species. In E. 

 micropora we have the relatively smaller size of the jaws, the great width 

 of the walls separating the convolutions of the alimentary canal, the walls 

 being in some places more than equal in width to the size of the alimentary 

 canal ; while in E. emarginata the Avails are narrow, scarcely equalling more 

 than half the width of the alimentary canal. In larger specimens the com- 

 parative length of the petals is not increased ; the edge of the test seems to 

 increase in width, and we find a greater distance between the extremity of 



