186 The Molluscan Family Planorhidae 



that at the i^oint of attachment to the superior jaw they are bent back- 

 ward more than usual. The jaw of Menetus opercularis is similar. 



The radula of Menetus cooperi callioglyptus (plate 67, fig. 3, from 

 British Columbia) has a large center tooth, higher than wide, the two wide, 

 spade-shaped cusps not reaching the lower border of the base of attach- 

 ment. The lateral teeth (1-8) are sciuarish and tricuspid, the cusps long and 

 spade-shaped, the mesocone the longest. The intermediate teeth (9-10) are 

 narrower than the laterals and have one or two additional cusps above the 

 ectocone. The entocone, mesocone, and ectocone become more nearly equal 

 in length. The marginal teeth (11-15) are very narrow, elongated, the ento- 

 cone is split into from two to four small cusps and the ectocone splits into 

 three to four small cusps. The outer marginal teeth are very narrow and 

 appear to be serrated with small cusps. The mesocone persists throughout 

 the entire series of teeth and may always be identified. 



Data for Radula 



Name Formula Locality Rows Collector 



cooperi callioglyptus 20-1-20 Quatsino, British Columbia 144-145 Mr. Arthur Peake 



cooperi 20-1-20 Orcas Ishmd, Washington 155-161 Dr. T. D. Foster 



The material for the study of Menetus was received from the following 

 sources: opercularis from Mountain Lake, near San Francisco, California, 

 collected by Mr. H. Walton Clark, two specimens examined; cooperi 

 callioglyptus, Quatsino Sound, Vancouver Island, British Columbia, col- 

 lected by Mr. Arthur Peake, eleven specimens examined; mill pond at 

 Crescent City, California, received from Dr. G. D. Hanna, four specimens 

 studied; cooperi, from Orcas Island. Puget Sound, small mountain lake on 

 Mt. Constitution, Washington, collected by Dr. T. D. Foster, fifteen 

 specimens examined. 



Specimens of cooperi callioglyptus from Quatsino Sound, Vancouver 

 Island, were largely infested with cercariae of trematode worms, as many 

 as 200 larvae occurring in one specimen. All organs were affected but the 

 ovotestis and albumen gland were more often attacked. The parasites 

 were most numerous over the stomach region. Specimens of cooperi from 

 Orcas Island, Puget Sound, had parasites in liver, ovotestis, albumen 

 gland, and over the stomach. In some specimens from both Washington 

 and British Columbia all of the organs were obscured by a thick coating 

 of mucus. 



Geographical Distribution. Tyjiical Menetus is distributed over the 

 Pacific coast region from Vancouver Island south to nortliern California. 

 The group does not extend far inland to the east. It is distinctively a genus 

 of the coast region. Only a few species are known. Opercularis appears 

 to be confined to California, but cooperi (=^ planulatus) is found from 

 northern California northward to Vancouver Island, and within this area is 

 cjuite variable. There are a number of local forms of limited distribution. 



Species Considered as Valid. The following species and races are at 

 present known for the typical subgenus of Menetus. 



Menetus opercularis (Gould) Menetus cooperi callioglyptus (Vanatta) 



Menetus cooperi F. C. Baker, new name Menetus cooperi multilineatus (Vanatta) 



for planulatus Cooper, 1859, not Menetus centervillensis (Tryon) 



planulatus Deshayes, 1824, a fossil 



species. 



