DORVILLEA CRASSA. 341 



The second somite wholly lacks tentacular chri or other appendages, like 

 the peristomium. It is of uniform length above and laterally, but is shorter 

 ventrally. 



The other metastomial somites bear parapodia. The third somite is shorter 

 than the second, the following ones decreasing to the fifth or sixth, with those 

 from this to the twelfth very short, after which a length greater than that of 

 the second somite is rapidly attained and maintained with little variation to 

 the end of the fragment (fifty first somite). The region of very short somites 

 {i.e., the fifth to twelfth) is the deepest part of the body as well as somewhat 

 the widest. All metastomial somites are strongly convexly arched above and 

 are flattened ventrally. There is a well-marked neural furrow along the venter, 

 this deepening caudad. 



The most anterior parapodia agree essentially with the others excepting 

 in being shorter. A typical parapodium from the anterior region is strictly 

 uniramous. It is more or less flattened in the cephalocaudal direction, is deeper 

 proximally than distally, and at the distal end bears two thin, distally rounded, 

 flaps extending entirely across the end of the parapodium, but not high. These 

 are the postsetal and presetal lobes and are essentially equal in size and alike 

 in form. Caudad these lobes become gradually lower and lower. All para- 

 podia bear neurocirri. Each neurocirrus is attached on the ventral side at the 

 base of the neuropodium. It is thick proximally, tapers conically, and nearly 

 attains the end of the neuropodium. All parapodia also bear notocirri. Each 

 of these is attached above at the extreme base. It is exceptionally stout, tapers 

 conically to an acute point, and in length conspicuously exceeds the parapodium. 

 Some of the notocirri are considerably flattened and all appear to have a large 

 axial blood-vessel. 



In each parapodium there is a single stout aciculum, which is colorless, or 

 in some cases slightly yellowish. Each is curved proximad of the middle, 

 with the concavity ventrad. The apex is acute, but not especially fine. On the 

 dorsal side of the aciculum in a typical parapodium there is a fascicle of simple, 

 strongly flattened, setae, each of which is apically bidentate and has a mem- 

 branous shield over the teeth. (Plate 62, fig. 7). Along one edge these setae 

 are finely serrate, the teeth or scales short. The setae on the ventral side of 

 the aciculum are much more numerous and form a more extended fascicle. They 

 are coarser than the dorsal ones and are all compound. In these the shaft 

 enlarges clavately from point of emergence distad to a little proximad of its 

 distal end, then again narrowing slightly to the oblique margin of the socket. 



