NO. 13 coe: revision of the nemertean fauna 307 



line wider than the others and extend forward to tip of head, while those 

 situated more laterally reach anteriorly only to brain region. Pigment 

 composing stripes extends into deeper layers of integument and is con- 

 spicuous in transverse microscopic sections. Ventral surface gray or 

 yellowish. 



Ocelli. Of moderate size, forming the corners of a square when head 

 is moderately extended. 



Proboscis. Proboscis large, provided with 10 nerves as in most other 

 members of genus; armed with comparatively large pear-shaped basis. 

 Stylet of about same length as basis. Each of the 2 lateral pouches con- 

 tains 2-3 accessory stylets. In the sexually mature type specimen the 

 basis measured 0.075 mm in length, 0.024 mm in diameter at anterior 

 end and 0.048 mm near posterior end. 



Cerebral sense organs. Large and highly differentiated ; situated near 

 anterior margins of brain and opening to ventrolateral surfaces of head 

 by pair of large canals. 



Nephridia. A single pair near middle of foregut region. 



Reproduction. Ova very large as compared with diameter of body. 

 Only a few are deposited at each ovulation, since the gonads become ripe 

 at different periods and each ovary produces but a single mature ovum at 

 any one time. 



Distribution. At present known from only a single specimen, which 

 was dredged at a depth of about 35 m at the northwest anchorage, San 

 Clemente Island, southern California. 



92. Tetrastemma signifer Coe, 1904 



T. signifer Coe, 1905, 1905a. 



Habitat. Among algae and other growths on rocks and piers near 

 low-water mark and below; also among kelp holdfasts at depths of 

 6-10 m. 



Distribution. At present known only from Monterey Bay and south- 

 ward to San Diego, California. 



Genus PROSTOMA Duges 



Only a single species, which is widely distributed throughout the 

 United States, has been found in fresh-water pools and lakes from Wash- 

 ington to California. This was presumably introduced from the eastern 

 states in association with cultivated water plants. 



