ONUPHIS COBRA. 303 



ously curved setae. These are, apparently, unjointed hooded crochets of the 

 bidentate type. The apical tooth is long, stout, and distally curved caudad; 

 the subapical tooth is very small and extends directly caudad. (Plate 52, fig. 8). 

 On the second parapodia long capillary setae of the type occurring on the more 

 typical parapodia make their appearance. The ordinary crochets first occur 

 singly, on the eighth somite in the paratype and at least as early as the tenth 

 in the type and probably similarly on the eighth. Farther caudad two crochets 

 appear in place of the one, the first somite on which the two were noted being 

 the nineteenth, though they may occur earlier, the rubbed condition of the speci- 

 mens preventing entire certainty. (Plate 52, fig. 7). The acicula have the 

 usual general form. Just after its emergence each is abruptly reduced to a fine, 

 acute tip. The medulla is strongly fibrillate distad to the exposed pale portion. 

 (Plate 52, fig. 4). The form of limbate setae is shown (Plate 52, fig. 5) and that 

 of the delicate pectinate setae in figure 6 of the same plate . 



In a typical parapodium of the middle or posterior region, each of the two 

 crochets are very long and of uniform diameter nearly to the region of the con- 

 stricted cervix, just below which it is curved, being elsewhere straight. Distally 

 it is bidentate, the teeth being long and acute; the subapical tooth is stouter 

 than the apical, and lacks an abrupt bend evident in the latter. The membran- 

 ous guards rise well above the level of the apical tooth and narrow to a point 

 distally. The medulla is strongly fibrillate distad as far as the cervix, and a few 

 short separate fibrillae are evident in the base of each tooth. The dorsal and 

 ventral Hmbate setae are similar in structure. Each presents a long, straight, 

 strictly capillary shaft and a short, abruptly bent, or geniculate, distal portion 

 which is bilimbate and attenuated to a fine acute tip ; the medulla is very finely 

 fibrillate and the wings are obliquely striate, as usual. The pectinate setae are 

 rather numerous, forming a conspicuous dorsal fascicle. They are dehcate 

 and transparent, and usually average about half the length of the exposed part 

 of a crochet. The distal expanded portion flares rather strongly, the distoectal 

 corner being prolonged and often curved back mesad. The teeth along the 

 free margin are short and uniform. 



The branchiae occur first on somite XV, each as a simple filament which 

 is very short, its length being more than once but less than twice the proximal 

 diameter of the dorsal cirrus. All the remaining branchiae are also simple 

 and cirrus-like, distinctly flattened. The second branchiae are broader than the 

 first and fully twice as long, equalhng half the length of the notocirrus, from the 

 base of which it springs, and also exceeding the greatest diameter of the latter. 



