TANAIDACEA AND ISOPODA -TATTERSALL. 239 



Station 348, off Barne Glacier, McMurdo Sound, 200 fathoms, bottom fauna, two 

 females and one male, 26-33 mm. 



Station 355, 77° 46' S., 166° 8' E., 300 fathoms, bottom fauna, fifteen females and 

 ten males, 24-38 mm. 



Remarks. — This species is very closely related to A. jjolaris, Hodgson, but may be 

 distinguished from that species by the different armature of the body, the longer second 

 antennae, and the longer terminal spines on the abdomen. 



In A. furcatus the longest and most conspicuous spines on the body are those on 

 the head, on the coxal plates and on the basal joint of the thoracic limbs. Thsre are 

 no specially large spines on the thorax, as in A. polaris, but the thorax and abdomen 

 are much more densely covered by small, sharp, backwardly directed spines than in 

 Hodgson's species. Studer's figure gives a very good general idea of the airangement 

 of these small spines. On the head there is a pair of long flattened and outwardly 

 directed spines, behind which is a row of small spinules. There is a prominent pre- 

 ocular spine on the antero-lateral corner of the head. 



The terminal spines of the abdomen are about one-sixth of the total length of the 

 body and equal to the terminal unsegmented portion of the abdomen. They are 

 therefore considerably longer, and in consequence more slender, than in A. polaris, 

 and rather longer than Studer's figure shows them. 



The second antennae are longer than the body, about one-sixth to one-fifth longer. 

 In a female measuring 38 mm. without the terminal spines of the metasome, the second 

 antennae measure 45 mm., the third joint measuring 5 "5 mm., the fourth 12 mm., and 

 the fifth 14 '5 mm. 



These measurements give a very fair idea of the general proportions of the second 

 antenna in this species, from which it will be seen that it is proportionately longer 

 than the same appendage in A. j^olaris. The second joint has a spine on the dorsal 

 face of the anterior margin and the outer distal corner produced into a strong spine. 

 There are three smaller spines about half-way along the joint on the dorsal and outer 

 face. The third joint has five small spines on the inner margin and five stronger 

 spines on the outer margin, in addition to the very strong spine on the outer distal 

 corner. The fourth joint has the outer distal corner produced into a strong spine. 

 The flagellum is composed of about fifteen joints. The third thoracic limbs have one 

 large and two smaller spines on the front margin of the second joint, the front distal 

 corner of the third, fourth and fifth joints produced into a strong spine, that of the 

 fourth the largest, the fifth joint with a smaller spine about half-way down. In the 

 fourth thoracic limb there are three spines on the second joint, and in the fifth five. In 

 the sixth to the eighth thoracic limbs, the second joint has about seven spines on the 

 inner posterior margin, and six on the outer posterior margin. The third joint has two 

 rows of small spines on the inner front margin, about eight in number. The inner 

 lower distal posterior corner is produced into a long spine, and there are three smaller 

 spines on the outer posterior margin. The fourth and fifth joints have two rows of 



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