314 



RUDOLF RUEDEMANN 



tli.f.l 



do 



'\ 



larger specimen, in natural size, on the horizontal plane. An 

 oblique view from above of the same specimen is given in Figure i 

 and a lateral view in Figure 2. The former presence of a cervical 

 fold in the Permian form, corresponding to that in recent species of 

 Apus (Fig. 4, where it is shown in the profile behind the eye), is 



indicated by a trans- 

 verse wrinkle, especially 

 distinct in the larger 

 specimen, but also seen 

 in the smaller one. This 

 wrinkle has resulted 

 from the yielding of this 

 transverse fold during 

 lateral compression. It 

 has thereby become 

 pressed downward and 

 changed into a deep 

 transverse wrinkle, in 

 front of which the cara- 

 pace has split and been 

 drawn inward. The 

 smaller specimen retains 

 the frontal portion in 

 more perfect form, 

 though also much com- 

 pressed. Owing to this 

 folding-in of the frontal 

 part, the perforations of 

 the carapace for the eyes 

 are not observable. 

 The shell-gland appears as an elongate elliptic body consisting 

 of two concentric furrows and one median and another outer 

 longitudinal one. There are thus altogether six urinary tubes 

 counted on the transverse line, just as in the recent Apus (Fig. 5). 

 All these are very distinct on both sides of the larger specimen and 

 also well recognizable on the smaller one. They bend inward and 



5. — Apus cancriformis Schaffer. Dorsal 

 From Parker and Haswell (after Bronn's 

 Thierreich). d.o., dorsal organ; E, paired eye; 

 e, median eye; sh. gl., shell-gland. 



Fig 

 aspect 



