2 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
regretted also that living material could not be had of all the species 
treated of, as descriptions. based solely upon alcoholic material are, to 
say the least, unsatisfactory, owing especially to the effect of reagents 
upon the pigments. 
The collections comprise five (?) species of Triclads and two Rhab- 
docoels. Three of these I hope to show are cosmopolitan in their 
distribution. 
Dendroccelum lacteum Orrsrep. 
Figures 1, 9-15. 
Dendrocelum lacteum OnrstED, 1844, p. 52. Woopworrn, 1896), p. 1048, 
Dendrocelum superbum GIRARD, 1851, p. 265; 18514, p. 2. 
Dendrocclum superbum Luipy (non Girard), 1852», p. 288. 
Dendrocelum pulcherrimum Girarb, 1851, p. 265; 18511, p. 2. 
Procotyla fluviatilis Stimpson (Leidy MS.), 1857, p. 23. DresixG, 1862, p. 517. 
Lerpy, 1885, p. 51. Harrez, 1890, p. 105. Grrarp, 1893, p. 164, Woop- 
WORTH, 1896, p. 95; 1896°, p. 241.1 
Procotyla leidyii GIRARD, 1893, p. 166. 
Station C; 13,166, “small pool on sandy margin of Thompson's Lake near 
Station G.” 
Color, milk white; creamy, yellowish, or, in larger, older specimens, roseate; 
no pigment except in eye-spots. Very translucent; intestine in all its ramifi- 
cations easily seen, grayish to brown or black according to the character of the 
contents, more deeply colored in larger specimens. A slight constriction 
immediately behind the plane of the eyes, marking off an anterior head end and 
producing the lateral projecting rounded cephalic appendages. Gradually 
widening posteriorly from constricted or neck region to a point about one 
sixth the total length from the anterior end, then margins are parallel to about 
one fifth the distance from the posterior end, tapering gradually from this point 
to the rounded posterior extremity. When in active motion and fully extended, 
the lateral margins are smooth and nearly parallel; but when partly contracted 
or at rest, the margins are very sinuous or crenate and thrown into folds, like 
the margins of many marine Planarians. A well marked median adhesive 
disk or sucker at the anterior end, the diameter of which is about one third the 
broadest diameter of the head. When the animal is in motion the shape of 
the anterior end is continually changing, owing to the protrusive and retract- 
ive movements of the disk, which can be protruded for a considerable distance, 
though projecting only slightly when in the retracted condition. Eyes usually 
two, but frequently accessory eye-spots from one to six in number. Distance 
between the eyes a little greater than from eyes to margin of head. Mouth 
opening (in preserved material) slightly posterior to a point midway between 
1 By a gross error I have in the above paper also referred to Keller und Tiede- 
mann’s Nordamerik. Monatsber. for 1851. 
