72 BULLETIN OF THE LABORATORIES 



extremity, where, after a shallow concave notch, the margin is convex. 

 The remainder or the margin is strongly convex. From the above 

 described ventral notch, a well defined, feebly convex, line passes 

 dorsad to the opposite margin. That portion of the shell which lies 

 cephalad of this line is usually curved laterad. From within the 

 cephalad and caudad extremities of the valves numerous hairs pro- 

 trude. 



In a dorsal view, the shell is sub- fusiform, being widest caudad 

 of the middle. At their caudad extremity the valves are slightly 

 divaricated, while at their cephalad extremity they are closely approx- 

 imated. The shell is covered with fine reticulations and minute hairs. 

 In addition to these, it is marked with conspicuous dark green bands. 

 These bands are arranged as follows : One, parallel to and almost ad- 

 jacent to the mesal border of the shell, extends from the caudo-ventrad 

 angle of the shell dorso-cephalad almost to the cephalad extremity of 

 the valve. There it divides. One portion continues in the same 

 course to the cephalo-ventrad extremity of the valve. The other, turn- 

 ing laterad, passes ventrad for a short distance and terminates in a 

 sharp point. At the origin of this line there is a large, convex blotch, 

 which extends ventrad a short distance. Near the centre of the figure 

 several bands fuse in such a manner as to form a hollow, sub-square 

 figure. From the cephalo-dorsad corner of the square a tongue passes 

 ventro-caudad into the square. The length of this tongue and the 

 angles it makes with the sides of the square vary slightly in different 

 individuals. Usually it extends almost to the centre. From this same 

 angle of the shell a band projects ectad. After passing cephalad a 

 short distance, this band forms a convex curve and passes caudo-dors- 

 ad almost to the margin of the shell. From the caudo-dorsad angle 

 of the square a short band passes dorso-caudad and fuses with a 

 broader band which passes caudad, approximately parallel to the dor- 

 sal margin of the shell. From this same corner another band passes 

 caudo ventrad almost to the caudad margin of the shell. This band 

 is approximately parallel to the band just described. From the caudo- 

 ventrad angle of the square a band passes caudo-ventrad almost to the 

 caudo-ventrad extremity of the shell. In the caudad portion of its 

 course this band curves dorsad, otherwise it is approximately parallel 

 to the band last described. From the cephalo-ventrad angle of the 

 square, a short band projects ventrad and then broadening, forms a 

 boot-shape band. The short heel of this boot projects caudad and 



