168 ALEPAS CORNUTA. 



and have their inner or posterior rami in an almost rudi- 

 mentary condition. In the sixth cirrus (PL X, fig. 28) 

 the outer ramus (a) has actually sixty-three segments, 

 whereas the rudimentary ramus (k) has only eleven, nearly 

 cylindrical segments. These are furnished with extremely 

 minute spines, of which those on the dorsal face are 

 longer than those on the anterior face ; the spines on 

 the summit of the terminal segment are the longest; 

 the segments are not half as thick as the normal ones in 

 the outer ramus. The rudimentary ramus is only one 

 seventh part longer than the pedicel which supports 

 both it and the normal ramus. In the fifth cirrus, 

 the rudimentary ramus is rather longer, and has thirteen 

 segments, resembling those in the rudimentary ramus of 

 the sixth. In the fourth cirrus there is no trace of this 

 peculiar structure, the rami being equal in length and 

 strength. The two rudimentary rami on each side are 

 nearly straight, and seem incapable of movement; they 

 project out behind the normal rami, and closely resemble 

 in general appearance, the two caudal appendages ; hence 

 this cirripede, at first sight, appears to be six-tailed. 



Pedicels of Cirri. — The pedicel of the first pair is very 

 short; that of the second is the longest; those of the pos- 

 terior cirri decreasing in length. Upper segments short ; 

 lower segments in the second, third and fourth cirri, irre- 

 gularly and rather thickly clothed with bristles, but in the 

 fifth and sixth cirri, there is a regular double row of main 

 spines, with some minute intermediate ones : hence there 

 is a difference, both in the rami and in the pedicels, between 

 the fourth cirrus and the fifth and sixth, and this is a 

 unique case. On the dorsal surface of the pedicel of the 

 second cirrus, there is a tuft of much feathered fine spines. 



Caudal Appendages. — Each consists of eight much ta- 

 pering, very thin segments, furnished with a few short 

 simple spines round their upper margins, and with a 

 longer tuft on the terminal short segment; basal seg- 

 ments twice as thick as the middle ones. In length, 

 these caudal appendages equal the pedicels of the sixth 



