COE: NEMERTEANS OF WEST AND NORTHWEST COASTS. 301 



white or colorless, provided with a similar transverse, deep brown 

 marking in both varieties. This cephalic marking (PI. 2, tigs. 16, 

 17) consists of a broad transverse band of color extending laterally 

 somewhat beyond the ocelli, and having a rounded and deeply bilobed 

 anterior margin. Sixteen pairs of rectangular brown mai-kings cover 

 most of the dorsal surface in the most common variety. Markings 

 usually very irregular in shape, in ordinary states of contraction 

 about one and a half times as long as broad, and separated medially 

 by a space about half as great as their own width. A pair of slen- 

 der, irregular, brown lines are situated on lateral margins of body 

 behind the head. Anteriorly these slender brown lines join the 

 more anterior rectangular markings, but at about 

 the third pair of rectangular markings become 

 separated, to join again at the fourteenth to six- 

 teenth pairs. Lateral lines often more or less 

 closely connected by bridges or completely fused 

 with the brown markings especially in the three 

 most anterior and three most posterior pairs of 

 markings (Text-fig. 61). When carried to the 

 extreme condition all the markings on body 

 back of head are fused with the lateral lines 

 giving rise to a second distinct variety, having 

 the whole dorsal surface back of head of a deep 

 brown color intei-rupted by about fifteen irregu- 

 lar transverse whitish bands extending toward 

 lateral margins (PI. 2, fig. 17) and indicating the 

 spaces between the sixteen pairs of rectangular 

 markings described for the first variety. Lat- 

 eral lines often completely lost in the rectangu- 

 lar markings, and both markings of the same 

 pair completely lose their individuality, some- 

 times leaving a paler median line. Sometimes, 

 moreover, the fusion is so complete that only a 

 portion of the full number of transverse whitish bands can be found. 



Ventral surface commonly dull grayish with a tinge of yellowish 

 in median hne ; often with numerous fine granules of brownish pig- 

 ment and with a greenish tint in intestinal region when filled with 

 ripe ova. • 



Ocelli of medium size and, as usual, arranged nearly in the form 

 of a square (PI. 2, fig. 17 ; Text-fig. 61). 



Fig. 61. — Tetrastemma 

 reticiilatitm. Outline 

 of anterior portion of 

 body, sliowing posi- 

 tion of oceUi and ar- 

 rangement of mark- 

 ings. X 40. 



