1903.] NATURAL SCIENCES OF PHILADELPHIA. 443 



swollen proximal and more distinctly articulated distal portion. The 

 extreme of these changes is exhibited by the 1st parapodimn, in which 

 both cirri are connate with the base of the neuropodium, than which 

 the neuropodial cirrus is twice, and the notopodial cirrus 3^ times as 

 long, the base of the former being cylindrical and twice the length of 

 the terminal piece, while the notopodial cirrus has the proximal end 

 much swollen, and the distal divided into 3 short joints. The second 

 parapodium differs from the first almost solely in the larger size of the 

 neuropodium. 



With the gradual reduction in size of the neuropodial cirri toward 

 the posterior end of the branchial region the basin-like form of the 

 ceratophore is gradually lost, and the whole parapodium assumes the 

 form peculiar to the posterior half of the body. The acicular lobe of 

 the neuropodium is so reduced in size that the ends of the acicula 

 project conspicuously beyond it. Still farther caudad the parapodia 

 become more pointed, their outhnes nearly continuous with the dorsal 

 and ventral curvatures of the body and the two cirri of approximately 

 equal length. The neuropodial cirri are stouter and more closely 

 united to the neuropodium, the notopodial still retain slightly enlarged 

 bases, but all appearance of articulation has gone. 



The branchiae are pinnate, the stem arising at right angle from the 

 base of the notopodial cirrus and curving parallel with the back toward 

 but not reaching the middle line ; the stiff, erect branches arise at regu- 

 lar intervals of about twice their own diameter, are subequal in length, 

 shorter and more slender than the cirrus, and the end of the main stem 

 bends upward as the last pinna. 



The following table shows the distribution of the branchiae and the 

 somites on which occur changes in the number of pinnse on the right 

 and left sides of both specimens : 



Type. Station 3,700. Cotype. Station 3,707. 



No. of Somite. Left. Right. No. of Somite. Left. Right. 



V 1 1 V 1 1 



X 3 3 IX + 3 



XI 4 5 X 4 4 



XIII 5 + XI 5 6 



XIV + 6 XII 6 + 



+ 



XVI 6 + XIV 7 



XVIII + 5 XVII ^ 



XX 5 + XXII 4- 



XXIII 4 4 XXV 6 



XXVII 3 3 



^XVIII 2 



XXIX + 



+ 



XXVII 3 3 XXVII 3 3 



XXVIII 2 XXVIII 



