164 CALIFORNIA ACADEMY OF SCIENCES, [Proc. 3D Ser. 



diameter of the body. Puberty-papillae varying in number, single, median, 

 never paired. The ventral interval between setae a-a slightly diminishing 

 from about somite XXIV to somite XVII. Penial setse with a few large 

 spines near apex. No dorsal pores. Prostomium divides somite I from one- 

 half to nine-tenths, and is furnished with two cross grooves. 



Habitat. — California: Calistoga, Napa County ; Mill Val- 

 ley, Marin County: also at Duncan Mills, Sonoma County; 

 on rather dry hill sides among manzanita bushes and other 

 native vegetation. My attention was first called to this 

 interesting form by Dr. H. W. Harkness, to whom my 

 thanks are due for many fine specimens. 



Affinities and Characteristics. 



Although this worm differs considerably from the other 

 Californian forms of the genus I do not consider it to be an 

 independent, well defined species — no more so than A. 

 ornatus 2inA A . -pa^illifer . These three forms are only 

 externally distinct, and so far as I can see agree in internal 

 structure. They appear to me as the beginning of species 

 branching from a common stock. With these exterior differ- 

 ences are connected differences in habitat. A.^afillifer is 

 only found in comparatively very moist places, generally in 

 heavy adobe soil, such as near streams, along ditches, under 

 logs, in flooded places. A. ornatus is found in less moist 

 places, in ordinary adobe soil, while A. collinus is found 

 only on dry hill sides, which are never exposed to excessive 

 moisture. I have nowhere found these forms intermingling 

 with each other in the same locality, and it appears as if 

 their external structure was due, in part at least, to their 

 different habitats. 



A . ^a^illifer resembles A . collinus in possessing only 

 unpaired median puberty papillge, while A. ornatus possesses 

 pairs of such papillas in the intersegmental grooves. In A. 

 ornatus and A . j)apillifer the structure of the genital zone 

 is the same, the male papilla being connected by a thin 

 transverse band, running in the short diameter of the body. 



