62 



G. 0. SAES. 



[No. 1. 



Explanation of the Plates. 

 Plate i. 



Fig. 1. Shell of an adult female specimen; from right side, mag- 



nified about 14 diameters. 

 Fig. 2. Same from above. 



Fig. 3. Adult gravid specimen of the first generation, with rather 

 fully developed young in the incubatory cavity; from left 

 side, magnified about 10 diameters. 



Plate II. 



Fig. 1. Adult female specimen of the second generation, with 

 less fully developed young in the incubatory cavity, the 

 animal completely withdrawn into the shell; from left 

 side, magnified about 24 diameters. 



Fig. 2. Another specimen of the later generations, without young 

 in the incubatory cavity but with greatly developed 

 ovaries; from right side, magnified about 20 diameters. 



Plate III. 



Fig. 1. Adult female specimen, with recently deposited ova in 

 the incubatory cavity and with head and tail fully ex- 

 tended; from above, magnified about 20 diameters. 



Fig. 2. Left adductor muscle of the shell (31), together with the 

 shell-gland; from outer side, magnified 56 diameters. 



Fig. 3. Preoral part of head; from above, magnified 50 diameters . 

 eye; oc ocellus; m levator muscle of antennæ; G coeca 

 of intestine; x rudimentary „affixing organ". 



Fig. 4. Cephalic part, from below ; same enlargement : oc ocellus ; 

 a 1 antennulæ; a 2 place where the antennæ are inserted; 

 L labrum; M mandibles; m 1 maxillæ of first pair; 

 m 2 maxillæ of second pair. 



