l82 E. A. ANDREWS. 



unusual height of the spine may be correlated with the height of 

 the annulus as variations of serially homologous structures, 

 whether there is any use for the spine or not. Returning to the 

 annulus we find in it the usual sperm-receptacle, of much the 

 same character as in the higher species and more complex than 

 in Cambarus cubensis. The mouth of the pocket is a sinuous 

 groove between elevated lips running across the convex ventral 

 face and extending a little distance onto the anterior and poste- 

 rior faces. Beginning on the anterior face, Fig. n, the narrow 

 mouth passes back from the middle line toward the left of the 



FIG. ii. Ventral face of annulus, lA. 



animal under the edge of a high, rounded tubercle. When the 

 annulus is seen from the front this tubercle is the highest point 

 of the annulus and from it the annulus slopes right and left 

 more steeply than is indicated in Fig. n. 



On the convex ventral face the mouth makes a U-shaped curve 

 to the animal's left and then a like one to the animal's right, to 

 finally pass onto the posterior face. Embraced in the second 

 curve is a second tubercle, less elevated than the anterior one 

 and on the opposite side of the mouth. On the posterior face 

 the mouth is seen as a short curved line coming down over the 

 edge about on the middle line and with quite an elevation on the 

 observer's right, close to the mouth. 



As is faintly outlined in Fig. n the pocket into which this 

 doubly bent mouth opens lies below it and not off to one side as 

 much as in C. cubensis , yet a more careful sketch, Fig. 12, 

 shows that the plane leading from the mouth to the bottom of 

 the pocket does slant somewhat and is not at right angles to the 

 surface of the annulus. Fig. 12 represents the sperm-pocket as 



