825] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. aL 
The color is sometimess bright orange anteriorly, but lighter posteriorly, 
with a faint dusky or greenish line along the middle. 
Another species, closely resembling the last in form, color, and size, is 
quite common under stones, and especially in dead tubes of Serpula, near 
low-water mark. This is the Cosmocephala ochracea V., (Plate XIX, figs. 
95, 95a ;) it has numerous eyes on the sides of the head, three or four 
on each side forming an anterior row parallel with the margin; the 
others forming two parallel oblique groups, usually with two or three 
eyes in each, farther back. On the lower side of the head there is, on 
each side, an obliquely transverse groove. The color is usually dull yel- 
lowish-white or grayish; the anterior part is often tinged with orange 
and the posterior with ash-gray ; there is generally a distinct paler me- 
dian line, most distinct anteriorly. It grows to be two or three inches 
long, when extended. 
Of the Planarians several species are also found creeping over the 
under side of stones and in the tide-pools. One of the most abundant 
is Procerodes frequens, which is a very small but lively species, found 
creeping on the under side of stones near high-water. It is usually 
about an eighth of an inch long, dark brown or blackish above and gray 
below, and it has two reniform eyes. The Jfonocelis agilis is still smaller, 
elliptical, with only one median eye; its color is dark brown or blackish. 
By some writers this genus is placed among the Nemerteans. Two 
larger species of this group are also occasionally found on the under 
side of stones. One of these, the Planocera nebulosa, (Plate XIX, fig. 
100,) is usually about half an inch wide and three-fourths long, but may 
become nearly circular, or may extend into a long elliptical form. It is 
flat and thin, with flexuous edges. Its color is olive-green above, with 
a lighter median stripe behind, and yellowish green below. The tenta- 
cles on the back are whitish and retractile. 
The Stylochopsis littoralis V., (Plate XIX, fig. 99,) is also frequently 
found on the under side of stones. It is remakable for having a clus- 
ter of eyes on.each tentacle, other clusters in front of them, and two or 
more rows of eye-spots around the margin, especially in front. Its color 
is variable, but usually greenish, greenish yellow, or brownish yellow, 
often reticulated with flesh-color; thereis generally a pale median streak 
posteriorly. The eggs were laid July 12th in large clusters, composed of 
many small white eggs closely crowded together, side by side, and at- 
tached to the surface of the glass jar in which they were kept. 
There are also representatives of the ‘round worms,” or Nematodes, 
to be found beneath the stones and among the roots of alge, hydroids, 
&c. Thecommonest of these is, perhaps, the Pontonema marinum (Plate 
XVIII, fig. 94.) This is a small, very slender, smooth, white, round worm, 
tapering to both ends, and very active in its movements, constantly coil- 
ing itself into a spiral and again uncoiling itself. Its head is furnished 
with about six minute cirri; in the male the tail is short, narrow, nearly 
straight, but one-sided, rapidly tapering. and subacute; in the female 
