NATURAL HISTORY. xci 



To the generic and specific characters given above we may add, that all the segments 

 of the body are produced inferiorly into long spines, that of the fourth being the 

 broadest and longest ; of the dorsal spines, the fifth and sixth are the longer. 



The femora of the three last pairs of legs are produced posteriorly into long spines, 

 and the penultimate segment has two spines. 



The first and second joints of the superior antennae are terminated above by a spine ; 

 the third joint is the shortest. 



The toe of the first foot is serrate, having about eight teeth, and the claw is clothed 

 with fine hairs on the exterior surface, as represented, highly magnified, in fig. 10', 



plate B. 



Plate B, fie. 8, represents a side view of Acant/ionotus cnstatus of the natural size. 



Fio-. 9, a magnified view of the upper part of the head and antennae. 



Figs. 10 and 11. Magnified view of the two first pairs of legs : and fig. 10' shows 

 the peculiar formation of the toe and claw of the first pair. 



Fig. 12. Magnified view of the three posterior segments, and middle plate of the 

 tail ; together with the lateral and temiinal styliform processes. 



Nov. Gen.— ACANTHOSOMA. {Owen, MS.) 



Char. Gen. — Antennce inequales, superiores dimidio breviores, articulo ultimo e plurimis segmentis 

 efformato, articulis tertiis et secundis superiorum sequalibus. Pedes 4-antici, monodactyli, fibformes, 

 articulo ultimo primi paris unguiculato. Kostrura productum acutum undulatum. Oculi parvi. 



16.— ACANTHOSOMA HYSTRIX. 



Char. Spec. — A. segmentis 9-anticis spinis septem armatis. 



This very distinct genus is more common at Felix Harbour than the preceding; it 

 was taken at Igloolik on a former voyage in considerable numbers. 



On each of the first nine segments of the body there are seven spines, forming in 

 the aggregate seven longitudinal rows, protecting the back and sides of the body ; in 

 addition to these there are two spines above the eyes, one on each side of the rostrum ; 



*M 2 



