202 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



General Remarks on Affinity. 



It is not without some hesitation that I have modified the 

 generic definition of this genus as given by Benham, in 

 order to be able to arrange in it the new species to be 

 described hereafter. On the other hand, if a new generic 

 name is to be made for our new species, its characterization 

 would rest mainly on negative characteristics, viz., the pos- 

 session of two gizzards instead of three, and on the lesser 

 extent of the clitellum. For the present, it seems prefer- 

 able to refer the new species to the old genus Trigaster , 

 and to modify the definition of the genus rather than to 

 create an uncertain one. The hidden nature of the sperm- 

 ducts is probably characteristic of all the species. 



The question will undoubtedly arise as to why this genus 

 has been made to include a species with only two gizzards, 

 when the genus was founded upon a species characterized 

 by three gizzards. The answer is found in the fact that 

 T. tolteca more closely resembles Benham's (3 and 13) 

 species T. Lankesteri than any other species or genus 

 known. It possesses all the important features of Benham's 

 species, the only great difference being in the number of 

 gizzards. Perhaps the most important character of Tri- 

 gaster will be found in the hidden course of the sperm- 

 ducts. While this is not demonstrated in T. Lankesteri, it 

 is more than probable that it will be found to be the case 

 even in this species. Benham did not find the sperm-ducts 

 and the probable reason for this is that they are hidden 

 in the body-wall. 



If the want of a gizzard should exclude T. tolteca from 

 the genus Trigaster , then a new genus must be created. 

 The species cannot be united with Benhamia, differing, as 

 it does, in too many important points. It possesses plecto- 

 nephridia instead of micronephridia; it has no diverticles 

 of the intestine; and finally, its sperm-ducts are hidden in 

 the body-wall. Za-potecia ameca-meccB resembles Benham's 

 original Trigaster species in most particulars, but differs in 

 having meganephridia instead of plectonephridia. 



