540 Illinois State Laboratory of Natural History. 



a 2, bear two rows of sense organs, and are faintly divided 

 marginally. 



VII is quadriannulate, the fourth ammlus being double ; 

 but as none of the other annuli show any indication of further 

 division the formula is regarded as b 1+6 24-a 2-f(6 5+6 6). 



VIII to XXIII inclusive are complete somites. In these 

 the relative 'widths of the annuli and the subdivision of 6 6 

 are not such constant and obvious features as in Dina fervida, 

 but careful measurements of a large number of cases show 

 the approximate equality of the first four annuli, while b 6 

 proves to be about twenty per cent, larger. In many of the 

 best-preserved specimens this relative proportion appears 

 with great constancy and regularity, but in others is more or 

 less obscured. In well-extended specimens a dividing furrow 

 cuts b 6 approximately into two equal sub-rings, but in con- 

 tracted examples this is also obscured by the development of 

 transient wrinkles as described for E. punctata. Of the more 

 distinct sensory papilla? there are on each ring from fourteen 

 to eighteen above and about an equal number of smaller 

 ones below. These are arranged in an irregular transverse 

 row along which smaller sense organs are scattered. 

 Frequently a median longitudinal dorsal tract is entirely free 

 from them, and they always become more evident marginally. 

 On a 2 the papilla? are usually more prominent, especially so, 

 as Bristol has observed, on some of the posterior somites. 

 On b 6 two rows of papilla? appear. These are especially 

 distinct at the margins of large individuals. 



XXIV is sometimes complete, and is always quinque- 

 annulate so far as observed. In most cases it differs from 

 the complete somites only in the relatively smaller size of 6 6 

 and the tendency, sometimes quite evident, for b 5 and b 6 to 

 unite on the ventral side. 



XXV is usually quadriannulate, sometimes only tri- 

 annulate, but it has been found impossible to find any in- 

 herent clue to the exact values of the annuli. Analogy with 

 other species would point to the first form as being composed 

 of b 1+6 2+a 2 -fa 3 ; the second, of a 1+a 2+a 3. 



XXVI is biannulate, the wide anterior annulus showing 



