ANNELID GENUS CAMBARINCOLA — HOFFMAN 353 



Spermatheca composed of three parts: An elongate, slender, 

 muscular walled ectal duct, which extends about halfway up the side 

 of segment v; a subglobose or ovoid ental bulb; and a small terminal 

 ental process composed of glandular cells. 



Variation. — The material which was studied from three localities 

 in Colorado is relatively homogeneous as regards structiu-e of the 

 jaws and reproductive systems, variations in these details being 

 largely a reflection of difference in size of the worms. It is quite true 

 that branchiobdellids are very variable in size after matm-ity, suggest- 

 mg continuous growth through life, and actual measurements carry 

 less significance than ratios of the measurements. 



Various combinations of measm'ements as functions of some 

 standard have been plotted graphically, and most of these show that 

 the material of macrodonta examined maintains a very constant set of 

 proportions despite changes in overall size. One suggestive detail 

 involves relative head size. Three specimens from Fort Collins, 

 Colorado, yield a head diameter to body diameter ratio of .60, .61, and 

 .62. In eleven other specimens from Boulder and Black Wolf Creek, 

 Colorado, the same ratio ranges from .71 to .99, with an average of .83. 

 These values, plotted along the hoiizontal axis of a chart with body- 

 length intervals on the vertical axis, separate out into two discrete 

 groups. Unfortunately, it cannot be ascertained whether we are 

 dealmg here with true geographic variation or with the effects of 

 preservation. Within a fairly wide latitude, the degree of contraction 

 or distention of a branchiobdellid after preservation is influenced by 

 the strength of the alcohol used. The foregoing example is introduced 

 to remark the likelihood that with uniformly preserved worms in 

 good series, a future student of the group will be able to cope with the 

 problems inherent in the study of soft-bodied, muscular animals. 



Affinities. — Cambarincola macrodonta is without doubt closely 

 related to C. philadelphica, and if the two occurred as sympatric or 

 adjacent aUopatric forms, it would be difficult to separate them with 

 confidence. In well-preserved specimens, the peristomial character 

 is most useful, but some individuals of 'philadelphica often do not show 

 the peristomial lobes, and it is easy to understand how various other 

 species have been misidentified by previous workers as macrodonta. 

 On the basis of my own limited knowledge of the species, I would 

 judge it to be an isolated, conservative remnant of the old late Tertiary 

 pre-philadelphica stock which has become isolated in the foothills of 

 the Rocldes by recent climatic events which have produced the now 

 semiarid nature of the Great Plains. 



Distribution. — This species has been recorded from 12 States 

 ra iging from New Mexico to Virginia, from South Dakota to Louisiana. 

 The specimens which I have been able to re-examine, those identified 



