230 CALIFORNIA ACADEMY OF SCIENCES. 



others, and may in such cases be used as an exterior 

 characteristic. The interior characteristics are the best 

 and surest. In the present state of our knowledge it can 

 hardly be said that the exterior characteristics are of 

 sufficient prominence to be used for determining the 

 species, except when coupled with interior ones. To the 

 already accustomed eye, almost every species shows cer- 

 tain peculiarities in shape, size and color, that may be 

 useful in assorting the worms, but these peculiarities are 

 not such as may be intelligently described and easily un- 

 derstood. 



Ocnerodrilus Beddardi n. sp. Figs, i, 14, 17, 18, 19, 



20, 27, 28, 29, 30, 32, 37, 40, 49, 55, 56, 74. 



External charactei's. The worm varies in length from 

 one and a half to two inches when fully extended. My 

 method to measure these and similar worms is to first kill 

 them in very weak alcohol, a few drops being added to 

 the water from time to time. When the worm is dead, it 

 should be at once taken out of the weak alcohol, straight- 

 ened out and then placed in a narrow glass tube with strong 

 alcohol. In this manner the undue contraction and bend- 

 ing of the worm is prevented, and the medium contracted 

 length may be measured. Ocnerodrilus Beddardi and O. 

 agricola are the two longest species of the genus known 

 so far. While their length is nearly double that of the 

 smallest species, O . occidentalis, the width of the body is 

 hardly wider than that species. Compared to this form 

 O. Beddardi \^ more tapering towards both head and tail. 



The clitelluni extends from somite xiv to somite xix, 

 encroaching on xiii, and sometimes not quite covering 

 somite xix. It is very much thickened above and on 

 the side, but in the immediate vicinity of the ventral 

 ganglion it entirely disappears. The spermathecal pores, 



