﻿SNAIL HOST OF ORIENTAL LUNG FLUKE — ^ABBOTT 



75 



sists at first of two minute, rough threads, increasing to 9 threads in 

 fourth whorl. Axial sculpture on each whorl consists of 11 evenly 

 spaced, raised ribs, which are slightly protractively slanting and are 

 crossed by the spiral threads to form 5 rows of tiny beads on each 

 rib. Kibs absent on lower half of whorl. Suture well indented. 

 Whorls moderately rounded. Umbilicus absent. Columella slightly 

 curved and thin. Outer lip thin and with a sharp, delicate edge. 

 The spire is cast at an angle of 80°. 



Measurements of a sample population from Geus River, Guam 

 Island (U.S.N.M. 590182) are given in table 1. 



A more detailed biometric treatment is presented in the section 

 dealing with bionomics (p. 99), and figure 82 is a graphic representa- 

 tion. Total shell length has been arithmetically plotted against the 



ANGLE OF SPIRE 

 29* 30' 31* 32* 33* 34* 35* 36* 37* 



9 II 13 15 17 19 21 23 25 



LENGTH (MInO 



Figure 32. — Correlation between length and width of shell and between angle of spire 



and width. 



width of the shell (solid circles). It will be seen from this graph 

 that the proportion of shell length to width, or the obesity, remains 

 essentially the same throughout life. The slightly more scattered re- 

 sults in larger specimens are probably accounted for by the fact that 

 stream erosion has worn down the first one or two whorls. The un- 

 broken line has been run through the mode of all the correlations. The 

 course of the dotted line has been run through only the six youngest 

 specimens, which showed little or no erosion, and has been protracted 

 farther on to what should be the proper and theoretical ratio for older 

 specimens. It will be noted that the majority of larger specimens 

 are above this dotted line, a phenomenon that has resulted from the 

 reduction of the total length of the older specimens by erosion. The 

 two circles that rest on the dotted line in the larger brackets were not 

 significantly eroded. A more detailed analysis of erosion and methods 

 for its correction have been presented in the section on bionomics 

 (p. 105). 



