302 MANUAL OF ZOOLOGY. 



free, thoradco-abdominal segments, the first and second (?) of 

 which bear one or more broad lamellar appendages upon their 

 ventral surface, the remaining segments being devoid of appen- 

 dages ; anterior rings united into a 

 carapace, bearing a pair of larval eyes 

 (ocelli) near the centre, and a pair 

 of large marginal or sub-central eyes : 

 the mouth furnished with a broad 

 post-oral plate, or metastoma, and five 

 pairs of movable appendages, the pos- 

 terior of which form great swimming- 

 feet : the telson, or terminal segment, 

 extremely variable in form ; the in- 

 tegment characteristically sculptured" 

 (Henry Woodward). 



The Eurypterida are all extinct, 

 Fig. 152. Larva of Limuius on and are entirely confined to the Pal- 

 ?e a r C Do n h g rn.f eatly "*****' (At " ^ozoic period. Many of them at- 

 tained to a comparatively gigantic 



size; Pterygotus Anglicus (fig. 151) being supposed to have 

 reached a length of probably six feet. In their characters they 

 present many larval features ; resembling the larvae of the Deca- 

 poda especially in the fact that all the free somites of the abdomen 

 (except the two anterior ones) were totally devoid of appendages. 



CHAPTER XXXIII. 



MALACOSTRACA. 



SUB-CLASS IV. MALACOSTRACA (Thoracipoda, Woodward). 

 The Crustacea of this sub-class are distinguished by the pos- 

 session of a generally definite nnmber of body-segments ; seven 

 somites going to make up the thorax, and an equal number 

 entering into the composition of the abdomen (counting, that 

 is, the telson as a somite). The Malacostraca are divided into 

 two primary divisions, termed respectively the Edriophthal- 

 mata and the Podophthalmata, according as the eyes are sessile 

 or are supported upon eye-stalks. 



DIVISION A. EDRIOPHTHALMATA. This division comprises 

 those Malacostraca in which the eyes are sessile, and the body 

 is mostly not protected by a carapace. It comprises the three 

 orders, Lcemodipoda, Isopoda, and Amphipoda. The eyes are 



