40 



Guide to Crustacea. 



Table-case shown being perhaps larger than the average, but in Arctic seas, 

 No- 5. where they are especially abundant, they often attain a much 



greater size, as is shown by the specimen of Diastylis goodsiri 



(Fig. 20) from the Kara Sea. 



Fig. 20. 



Diastylis goodsiri, female, from the side, enlarged, a.', antenuule ; l.^-l.^, the 

 five pairs of walking-legs ; m., brood-pouch ; ps., " pseudo-rostrum," 

 formed by lateral plates of the carapace ; t.. telson ; ur., uropods. (From 

 Lankester's " Treatise on Zoology," after Sars.) 



Table- case 

 No. 6. 



Order 3. — Tanaidacea. 



Six of the thoracic somites are always distinct, the reduced 

 carapace involving only the first and second (Fig. 21). On each 

 side the overhanging carapace encloses a cavity within which lies 



sc- 



FiG. 21. 



Apseudcs sjnnosus, female, from the side, enlarged, ex., vestiges of exopodites 

 on second and third thoracic limbs ; oc, the small and immovable eye- 

 stalks; sc. , scale or exopodite of antenna; /(;■., uropod. (From Lankester's 

 "Treatise on Zoology," after Sars.) 



(as in the Cumacea) a branchial appendage attached to the first 

 thoracic limlx The second thoracic limb is chelate or pincer-like, 

 and the second and third may carry minute vestiges of swinnning- 

 branches (exopodites) (Fig. 21, ex.). The eyes, when present, are 

 set on siiiiill ;uul iiiiniovable stalks (Fig. 21, oc). 



