Z BULLETIN : MUSEUM OF COMPAKATIVE ZOOLOGY. 



regretted also that living material could not he had of all the species 

 treated of, as descriptions based solely upon alcoholic material are, to 

 say the least, unsatisfactory, owing especially to the efiect 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. 



DendrocoelurQ lacteum Oersted. 



Figures 1, 9-15. 



Dendroccelum lacteum Oersted, 1844, p. 52. Woodworth, ISQG'', p. 1048. 



Dendrocodum superbuiii Girard, 1851, p. 265 ; 1851% p. 2. 



Dendroccelum superhum Leidt (non Girard), 1852'', p. 288. 



Dendrocodum pulcherrimum Girard, 1851, p. 265 ; 1851", p. 2. 



Procotyla Jluviatilis Stimpson (Leidy MS.), 1857, p. 23. Diesing, 1862, p. 517. 

 Leidt, 1885, p. 51. Hallez, 1890, p. 105. Girard, 1893, p. 164. Wood- 

 worth, 1896, p. 95 ; 1896% p. 241.1 



Procotyla leidyii Girard, 1893, p. 166. 



Station C ; 13,166, " email 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 marguis 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. 



