1909.] FROM THE BAY OF BISCAY. 873 



apical joint with long setas, the others with only 3 or 4 small setae 

 apiece. 



The Irish specimens of 8-9 mm. agree with the ' Huxley ' one ; 

 the sensory filaments and calceoli are developed, though in much 

 less degree than in the adult. The larger males, 10 mm., have 

 the peduncle joints of the inferior antenna as figured by Sars ; 

 the 4th joint being three-quarters the length of the 5th, instead 

 of subequal to it, as in the younger animals ; flagellum 36-jointed. 



In the young in the incubatory pouch the 4th and 5th joints 

 of the peduncle, taken together, much exceed the flagellum in 

 length. 



The calceoli are of exactly the same construction as those 

 figured by Bonnier for B. rostrata, but with the " cuj^ule " much 

 smaller in proportion to the " tube." They are a character of 

 sexual maturity, appearing simultaneously with the incubatory ^ 

 lamellfe in the female, and with the antenna] sensoi-y filaments in J 

 the male, and increasing in size and number with the animal's 

 gi-owth. 



Oral parts : upper Up. — The apex appears to be more pi"oduced 

 in the male than in the female ; apical margin covered with fine 

 minute hairs, with a cluster of longer ones on either side. 



Mandibles. Female (fig. 54) : Bight mandible. — Cutting-plate 

 greatly curved ; margin divided into 8 rounded teeth, with 1 large 

 obtuse tooth above, and 2 very large teeth below. Accessor^/ 

 plate tridentate, upper tooth at a different level from the others, 

 as appears usual in this genus. Left mandible. — GiMing-jdate 

 with 1 large tooth above, 7 small rounded ones, and 2 strong- 

 incurved teeth below. Accessory p)late much stronger than that 

 of the right mandible, margin divided into 6 teeth. 5 spines in 

 the spinerow., each with a delicate brush-like seta behind. The 

 spines are stout, and being covered with minute spinules, have a 

 downy or furry appearance. Molar prominent, the small spines 

 edging the crown of the same construction as those of the spine- 

 row ; crown surrounded with numerous long fine setas. 



Male. — Cutting -plates tridentate below, margin divided into 

 9 rounded teeth ; accessory jjlcotes as in female, 4 spines in spine- 

 row in ' Huxley ' specimen, 5 in Irish specimens of 10 mm. 

 length. 



The terminal joint of the jm^P is covered on the outer side 

 with a fur-like spinose armature. The margin is bordered with 

 three series of spines ; an apical group of 3 or 4, long and seti- 

 form ; then a group of shoi't, flat, strongly dentate spines (fig. 59), 

 usually 5 on the right palp and 6 on the left ; the thiixl series 

 extending along the re.st of the mai-gin. containing 18-20 spines 

 of varying length, similar to but smaller than those at the apex 

 (fig. 60). The spines of the 2nd joint are of the cleft-tipped 

 variety, feathei-ed for half their length. 



Maxilla 1. Female and male. — Outer plate with 9 spines set 

 in two rows ; 5 with from 1-3 large auxiliaiy teeth ; the other 4 

 longer, with from 4-12 small teeth (fig. 55). The number of spines 



