76 HAWAIIAN AND OTHER PACIFIC ECHINI. 



Mellita. 



Agassiz, 1S41. Mon. Scut., p. 34. 

 T.Npr, SciikUn quinquejom Lamarck, 1S16. Anim. sans Vert., 3, p. 9 = Echinodisnis quinqucspcrforatus 



Leske, 1778. Add. ad Klein, p. 133. 



Like the preceding this is strictly an American genus but whereas two thirds 

 of the species of Encope occur on the tvest coast of tropical America, two of the 

 four species of MelUta occur on the east coast. These clypeastroids give every 

 indication of high specialization, not only in the extreme flatness of the test with 

 the accompanying peculiarities of lantern and auricles, but in the lunules, the 

 position of the periproct and even in the spines and pedicellariae. The spines 

 are soUd and the primaries are more or less swollen at the tip (PI. 125, figs. 17, 

 18) ; they may be somewhat cm•^'ed, while many of the miliaries are abruptly 

 bent (PI. 125, fig. 16). The pedicellariae are greatly reduced in size and number 

 and no ophicephalous are to be found. All have but two valves and these are 

 of pecuhar shape. Calcareous particles in the pedicels seem to be nearly or 

 quite wanting; sometimes a few small rods may be present. The lunules afford 

 the best characters for separating the species, both the number and the size and 

 form being of real importance. There are four species which seem to be valid. 



Key to the Species of Mellita. 

 Lunulas 5. 



Interambulacral lunule very variable in length but usually less than .20 test- 

 length, and seldom much longer than posterior ambulacral lunules; if imus- 



ually long its breadth will be .1.5-.20 of its length quinquiesperfomta. 



Interambulacral lunule long and very narrow, from .2.5 to .40 test-length and 

 40-100";^ longer than posterior ambulacral lunules; its breadth is less than 



.10 length longifissa. 



Lunules 6. 



Interambulacral lunule long and narrow, its length at least twice and usually 



several times its own breadth sexiesperforala 



Interambulacral lunule broad and rounded, its length only about 2.5 '^'J, more 



than its breadth pacifica. 



Mellita quinquiesperforata. 



Echinodiscus quinquiesperforatus Leske, 177S. Add. ad. Klein, p. 133. 



Mellita quinquiesperforata Meissner, 1904. Bronn's Thicr-reichs, 2, abt. 3, buch 4, p. 1384. 



Plate 125, figs. 16-21. 



Pechcellariae are very scarce but the bidentate at least are quite character- 

 istic. The valves are only .12-.1S nun. in length ; they are somewhat compressed 



