158 MR. R. COLLETT ON ECHIDNA ACANTHION. [Feb. 3, 



membranous tissue. One (the left ?) was the larger, and had a 

 length of about b7 millim., a breadth of 40 millini. ; its greatest 

 thicliness (at the outlet of the lacteal ducts) was 22 millira. The 

 other was a little smaller. 



The "mammary areola" was visible on the belly as a flattish 

 spot. No trace of a pouch could with certainty be distinguished 

 (in the single mounted female specimen). 



In the mounted fuU-giown male was visible on each side of the 

 belly (where the mammary areola is found in the female) a small 

 vortex of hairs, apparently an indication of the rudimentary mamince 

 of the males of other mammals. 



Parasites. — In two specimens I found half a dozen individuals of 

 an Ixodes, attached between the hairs at the root of the dorsal 

 spines or in the ear-tuft. 



Companson with E. aculeata. — Whilst E. acanthion will be easily 

 distinguishable from E. aculeata by its external characters, the 

 skeletons of both species are more difficult to distinguish. Yet, 

 compared with a skeleton of E. aculeata of the same size, that of 

 E. acanthion will be seen to be decidedly slenderer. 



Thus when the skeleton No. 3, with a total length of 448 millim., 

 is laid side by side with a skeleton of E. aculeata, the total length of 

 which is 450 millim., all the vertebras from the head to the pelvis show 

 themselves as perceptibly narrower and weaker ; whilst the breadth 

 of the penultimate lumbar vertebra in E. aculeata was 20 millim., 

 the same vertebra in E. acanthion was only 16^ mdlim. broad. 



The processus spinosi of the first dorsal vertebra did not (yet) 

 show any trace of being notched in E. acanthion, whilst the notches 

 were distinct in the other species. 



The humerus is weaker and narrower. The breadth between 

 epicotidylus medialis and lateralis (i. e. the greatest breadth on the 

 ulnar side) is in E. aculeata 4/ millim., in E. acanthion 41 millim. 

 only ; the breadth between trochanter medialis and lateralis {i. e. 

 the greatest breadth on the scapular side) is 31 millim. in E. aculeata, 

 and 27 millim. in E. acanthion. 



The scapula is shorter and is more straight. Its greatest length 

 (to the articulation with humerus) in E. aculeata is 56 millim., in 

 E. acanthion 51 millim. ; in the latter species the margo superior 

 is almost straight, but more bent outwards in E. aculeata. 



The ribs are not narrower in E. acanthion than in the other 

 species ; but the pelvis is decidedly weaker. Whilst thus the length 

 from the upper end of os ilii to the hinder end of as ischii (i. e. the 

 greatest length of the pelvis) in E. aculeata was t)6 millim., the 

 same distance in E. acanthion was (JO millim. only ; and whilst the 

 greatest breadth (between the upper ends of ossa ilii) in E. aculeata 

 was 44 millim., the same in E. acanthion is 41 millim. Also the 

 foramen obturatorium was the larger in E. aculeata. 



The/emwr is shorter; m E. aculeata its length is 59 millim., 

 in E. acanthion 53 millim. Any difference in the length of the 



