590 Verrill, JVotes on Hadiata. 



Meoma grandis Gray. 



Meoma grandis Gray, Ann. and Mag. Nat. Hist., vii, p. 132, 1851 ; Cat. Ech. Brit. 

 Mas., p. 56, Pi. 5, fig. 2, 1855 ; A. Agassiz, Bulletin Mus. Coaip. Zool., i, p. 275, 1810. 

 Kleinia nigra A. Agassiz, Bulletin Mus. Comp. Zool., p. 27, 1863. 

 Meoma nigra Verrill, these Trans., p. 317, 1867; Amer. Jour. Sei., xlix, p. 93, 1870. 



Of this interesting species there are ten specimens in the collection 

 from La Paz, which show considerable variation from the type form- 

 erly described by me, as well as among themselves. 



The largest is 4-85 inches long, 4-25 broad, 2-10 high; the smallest 

 3-85 long, 3-40 broad, 1 '75 high. The outline, as seen from below, 

 varies but little and is broad-oval, somewhat emarginate anteriorly, 

 obliquely truncate posteriorly, and slightly compressed laterally, or, 

 in other words, nearly heart-shaped. The anal area is large, some- 

 what sunken, and is at the extreme posterior end of the shell, occupy- 

 ing the greater part of the truncated portion. Its form varies from 

 regularly elliptical, acute ^t each end, to broad-oval, rounded below 

 and acute above ; its position varies from nearly vertical to decidedly 

 oblique, and it is so nearly terminal as to produce a posterior emargi- 

 nation in a dorsal view of the shell. In a side view some specimens 

 are decidedly depressed, but most are regularly arched, while one is 

 decidedly elevated at the apex. There is considei'able variation in 

 the depth of the anterior ambulacral groove, and also in the number 

 and prominence of the large tubercles, which are more or less 

 restricted to the region enclosed by the peripetalous fasciole. The 

 fasciole itself shows remarkable variations, but does not agree at all 

 with Gray's figure. The portion crossing the anterior interambula- 

 cral regions varies less than other parts, biit in some the intermediate 

 transverse portion is nearly straight, in others strongly curved and 

 often crooked, in one it is bent up into a right angle on each side of 

 the ambulacral groove ; its bend or angle near the antero-laterai 

 grooves is also variable, both in form and extent, it being twice as 

 large in some specimens as in others, and in one an irregular, crooked 

 branch passes from the apex of the angle on the left side to the ante- 

 rior groove. In the posterior interambulacrum the coarse of the fas- 

 ciole is quite variable, in five examples it crosses with a strongly 

 curved upward bend, without any distinct angle, lising highest in four 

 spL'cimens on the right side, in the other forming a nearly straight 

 transverse middle portion ; in three specimens it forms a sharp angle on 

 the right side ; in one a similar angle on the left side ; in another there 

 is a strong median angle, its apex pointing to the anal region, and 

 another to the right of it, pointing to the summit ; in all the speci- 

 mens it bends inward farther than in Gray's figure. The lateral part 



