292 CALIFORNIA ACADEMY OF SCIENCES. 



village. The bottom of the pond consists of a black 

 sticky mud which is at the edges of the pond interwoven 

 with projecting palm-root fibers. Among these in the 

 mud the worm was found. Unfortunately I had only a few 

 minutes to spend in collecting and the worm being scarce 

 I found only a dozen specimens in all, most of which 

 were immature. This was in March of last year. In 

 size and form the worm greatly resembles Ocnerodn'/us 

 Beddardi, though when it was alive there must have 

 been some distinguishing features, as my notes made at 

 the time of discovery read: " Differs in general appear- 

 ance from the common Ocnerodrilus of the region be- 

 ing perhaps a little thicker in front and also a little 

 flatter.'' 



The occurence and distribution of these minute oli- 

 gochaeta are frequenly restricted and unaccountable. In 

 the San Jose del Cabo Region I found generally in every 

 moist place only Ocnerodrilus Beddardi and no other 

 form. In this pond, situated in the center of that region, 

 a new genus suddenly looms up, and is found nowhere 

 else in that vicinity. 



With species of Ocnerodrilus the same limited distribu- 

 tion is noticeable. Thus the only California species of 

 this genus is Ocnerodrilus occidental is which to date has 

 only been found in a single garden, one hundred feet 

 square, and strange to say five years previous to the first 

 finding of this species, the locality in question was in the 

 midst of a desert with not a drop of permanent water 

 within twenty miles. It is reasonable to suppose that 

 the worms were brought down by irrigation water, but 

 though I searched repeatedly along the source of the 

 water supply and along the canals I could not find them 

 outside of the original locality. These instances could 

 readily be multiplied. Some species have a wide dis- 



