REPORT ON THE MYZOSTOMIDA. 
23 
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Border of the disk with cirri. 
Ten cirri on each side. 
Cirri very short, body stout and opaque ; mostly very big, with 
a vaulted hack. 
Body oblong, extended, with a keeldike back, laterally com- 
pressed, ....... 
Body disk-like. 
Body muchjonger than broad, flat above and below, 
Body circular, length and breadth equal, or nearly equal. 
Central muscle-mass striking : 
Occupying the whole border of the belly ; back flat, 
A marginal zone free ; back vaulted. 
Back covered with warts, .... 
Back irregularly areolated, without warts, 
Central muscle-mass not striking. 
With a distinct hyaline marginal border. 
Parapodia small, lying in small cavities, 
Parapodia well-developed, freely projecting, 
A hyaline marginal border not existing. 
With five pairs of dorsal elevations, . 
Back without elevations. 
Parapodia very feeble, quite close to the border, 
Parapodia well-developed, removed from the border. 
Cirri distinct, many times longer than broad. 
Body very big and massive, back with scattered 
tubercles, .... 
Body of insignificant size, without warts. 
Diameter of more than 9 mm. ; parapodia in 
the first third of the radius, 
Scarcely half as big ; parapodia in the middle 
between centre and border, 
Cirri reduced to insignificant warts, 
Cirri (mostly) long ; body generally a thin, transparent, delicate 
plate. 
Middle part of the body two-coloured, . 
Middle part of the body one-coloured. 
The whole body opaque, stout, black-brown, . 
The whole body, or at least the border, pellucid, delicate. 
With marginal fringes besides the cirri, 
Without marginal fringes. 
Hind end deeply intersected, .... 
Hind end bordered, rounded. 
Cirri reduced to warts, .... 
Cirri well-developed, long. 
Cirri much different in length (the first and tenth 
pairs often longer than the others), 
Cirri not much different. 
Border notched, . 
Border not notched. 
Cirri ending in fine points, 
M. cornpressunu 
J /. areolatum. 
M. radiatum. 
M. marginatum. 
M. lutkeni. 
M. brevipes. 
M. pallidum. 
M. testudo. 
M. carpenteri. 
M. gigas. 
M. coriaceum. 
M. triste. 
M. glabrum. 
M. pictum. 
M. nigrescens. 
M. fimbriatum. 
M. excisum. 
M. brevicirrum. 
M. antennatum. 
M. crenatum. 
. M. agassizii. 
