CRUSTACEA SYSTEMATIC REVIEW 



293 



...u 



Ml 



to the racial form of the Malacostraca, and is often placed as a special sub-class 

 between the Entomostraca and the 

 Malacostraca. Body slender, covered 

 with a bivalve shell, which extends 

 back, leaving only the last 4 abdo- 

 minal segments free. Besides this 

 there is a movable cephalic plate. 

 Head, with the 5 typical pairs of 

 appendages, distinct from the thorax. 

 All the 8 segments of the short 

 thorax are distinct, with 8 pairs of 

 similar biramose lamellate feet. On 

 the basal joint of the protopodites of 

 these segments there is a large epi- 

 podial lamella functioning as a gill. 

 The 4 anterior pairs of pleopoda 

 are strong biramose rowing feet, the 

 2 posterior pairs are short and uni- 

 ramose. The last segment of the 

 abdomen carries two furcal processes. 

 On the head are 2 stalked compound 

 lateral eyes. Heart elongated, with 

 7 pairs of ostia, stretches through 

 the thorax and the abdomen as far 

 as into the 4th abdominal segment. 

 Masticatory stomach present. 



Single order and family, Ncba- 

 lidce: Nebalia (Fig. 196), Parane- 

 balia, Nebaliopsis, marine forms. 



The fossil Paleozoic forms Cera- 

 tiocaridce (Archoeostraca), Hymen- 



ocaris, Ceratiocaris, etc., are probably related to the Lepto- 

 straca. 



Legion II. Arthrostraca (Edriophthalmata). 

 A shell fold is wanting, except in the division of the 

 Anisopoda. The first thoracic segment (less frequently the 

 second also) is fused with the head, and the foremost pair 

 of thoracic feet are transformed into foot -jaws. The 2 

 lateral eyes are sessile. 



Order 1. Anisopoda. Fia 19( 3. Nebalia Geoffroyi, male (after Claus). 



r, Rostral plate ; c, cephalic region ; km, masticatory 



First and second thoracic seg- stomach ; md, mandible ; sm, shell muscle ; mxt, feeler 

 ments fused with the head. Cephalo- of the anterior maxilla (cleaning foot) ; I- VIII, thoracic 



thorax with lateral shell fold, which se S ments .; . testes 5 s > shell /> heart 5 d > intestine; 

 ... a i> anterior, a-->, posterior antenna ; mt, mandibular 



on each side covers a respiratory feeler . 6r/j thoracic feet ; p rP6} pleopoda ; , eye. 

 cavity. Both the pairs of maxillse 



have feelers. The feelers of the anterior -pair project into the respiratory cavity 

 as cleaning appendages. The maxillipede has an epipodial appendage functioning 

 as gill. The pair of limbs belonging to the second thoracic segment, which is 

 also fused with the head, are developed as powerful forceps. Abdomen with 

 biramose swimming feet. Heart in the thorax, generally with 2 pairs of ostia (the 

 heart of Apseudes has only 3 ostia). Apseudes, Tanais, Leptochelia. 



