442 PKOCEEDINGS OF THE NATIONAL MUSEUM vol.89 



common northern species. But as similar tests are in the Museum 

 of Comparative Zoolo<jy from "off Nantucket," whereas the species 

 is not known to live farther north than Chesapeake Bay, it may be 

 these bare tests from Maranhao need not be construed as evidence 

 that quinquiesj>erforata really occurs living on the Brazilian coast. 

 Obviously the actual -ecological relationships of latiarribulacra and 

 quinquiesperforata are completely obscure. 



MELLITA QUINQUIESPERFORATA TENUIS,' new variety 



Plate 60, Figure 2 ; Plate 61, Figtjre 2 



Descriplio7i. — Test notably light and thin, very nearly circular but 

 somewhat narrower anteriorly and with slight reentering curves at 

 each end. The diameter along different axes ranges from 103 mm. 

 through III-5 to 109 mm. through 1-3, but the usual measurement 

 is about 107 mm. Apex posterior to abactinal system, at or a little 

 posterior to center of test; at that point the test is almost 10 mm. 

 high. The slope from margin to apex is quite uniform and gradual 

 from all sides; the margin in III is barely 2 mm. thick and in 5 it 

 is just 1 mm. Genital pores 4. Petaloid area of moderate size, 

 about 58 mm. long by 55 mm. wide; unpaired petal (ocular pore to 

 tip) 25 mm. long by 14 mm. wide, narrowed at tip and but little 

 open there; petals II and IV 24 by 12 mm,, narrowly open, the inter- 

 poriferous areas quite straight; petals I and V 30 by 15 mm., nar- 

 rowed at tip and scarcely open there. Lunules strikingly small and 

 straight; II and IV 10 mm. long by 2.5 mm. wide, I and V 11 by 

 2.5 mm., and the unpaired lunule 18 by 3.5 mm., its posterior end 

 20 mm. from the test margin. Periproct very long and narrow, 

 4.5 by 1.25 mm,, its anterior margin only 3.5 mm. from the posterior 

 margin of the peristome, which is small, rounded-pentagonal, only 

 3 mm. in diameter; the ambulacral knobs are small and incon- 

 spicuous. Ambulacral furrows of oral surface well marked, but the 

 intermediate areas are rather narrow; in II and IV these areas are 

 47 mm. long but only 21 mm. in maximum width. 



Primary spines of dorsal surface less than 1 mm. long, very slender 

 at base but swollen at the tip into a conspicuous ovoid head about 

 one-third the length of the entire spine. Surrounding the lunules 

 and around the margin of the test the primaries are elongated, nar- 

 row, flattened, and blunt, but they are not widened at the tip, rather 

 they may be narrowed. On the oral surface the primaries are slender 

 and elongated and arranged so that they lie almost horizontally and 

 pointing in definite directions, as in the other species of Mellita. 

 No pedicellariae have been detected. 



*Te»Mij» = thin, in reference to the texture of the test as compared with that of the 

 species itself. 



