AUTOLYTUS OBLIQUATUS. ' 109 



The first somite, or the region morphologically representing it, bears two 

 pairs of tentacular cirri, of which the dorsal on each side much exceeds the ventral 

 in length and thickness; though itself not long, reaching only to the third or 

 beginning of the fourth setigerous somite, the ventral one scarcely reaching to 

 the second. The annuli are vague. (Plate 20, fig. 1,2). 



The second somite bears on each side a small neuropodial tubercle which 

 shows no setae. Above this is a very large tentacular cirrus of very nearly the 

 same form and size as the median tentacle, thus greatly exceeding the other 

 tentacular cirri. 



The third and succeeding somites are setigerous. The first six setigerous 

 somites are sharply set off from the rest of the body as a distinct region. These 

 somites are all dark in color, from the contained masses of spermatozoa which 

 crowd the parapodia, including the proximal region of the notocirri, as well as 

 the somites proper. They are further distinguished by their short, subcorneal 

 parapodia directed laterad and bearing only the short, stout composite setae. 

 The first pair of these parapodia are more slender than the others. The notocirri 

 are short, a little surpassing the setae, and are swollen proximally as shown in 

 the figures. (Plate 19, fig. 8; Plate 20, fig. 1, 2). 



The second and much larger division of the body is sharply differentiated 

 by its transparency. The parapodia are much longer and are directed usually, 

 at least in preserved specimens, caudoectad, though often in part cephaloectad. 

 They are deep dorsoventrally, but thin and compressed anteroposteriorly, with 

 the anterior face convex, or flat, and the caudal flat, or more or less concave. Dis- 

 tally each parapodium is bilobed, with the depression between the two lobes weak, 

 the dorsal lobe the larger. On each lobe there is a low but relatively wide, thin, 

 transparent, postsetal lip. The dorsal lobe bears long simple setae, the ventral 

 one only short, stout, composite ones like those of the anterior division. The 

 notocirri are transparent, all short, cylindric, and attached far distad. No anal 

 cirri were detected in any of the specimens. (Plate 20, fig. 1). 



The composite setae in the anterior parapodia appear to average near 

 twelve in number. Each has the shaft gently curved, especially distad of the 

 middle, and abruptly stronglv enlarged at the distal end, where it forms the 

 socket; the distal edge is oblique, with few fine pointed teeth on each side and 

 at the apex with a much larger one. The distal piece is of the usual general 

 form. At the tip it is bidentate, the teeth moderately oblique, short, and not 

 very acute, subequal, but the lower more commonly somewhat the larger. The 

 simple capillary natatory bristles as usual are numerous, long, and very fine at 

 the tips. 



