i6o 



SYSTEMATIC ZOOLOGY 



covered by a carapace. There is always a pair of compound 

 eyes, which are sometimes sessile and sometimes stalked. The 

 internal anatomy of the Malacostraca offers one distinguishing 

 point in the structure of the stomach, which is provided with an 

 apparatus for grinding the 

 food ; this is never found in 

 Entomostraca. In their de- 

 velopment the nauplius stage 

 is passed in the egg mem- 

 brane, and the larva hatches 

 in a later stage of develop 

 ment ; in a few cases there is 

 no larval stage. The Mala- 

 costraca may be divided into 

 three subclasses. 



SUBCLASS I. LEPTOSTRACA 



The Leptostraca (Gr. \e7r- 

 T09, delicate, and oarpaKOv, 

 shell) constitute a very small 

 group of minute marine Cms 

 tacea, which are interesting 

 and important as forming a 

 connecting link between some 

 of the Entomostraca, such as ' "■ x 52. Nebalia 



.-u tji 11 j 1 .1 geoffroyi. Male; 



the Fhyllopoda, and the ,,,,,„,, enlarged, a, 

 higher Malacostraca. Thev eye; "»• antennule : 



J ,].,, antenna; c, head; brf, 



present the exception to the thoracic feet; ,/, intestine; 

 constant number of segments *■ heart; *"*■ s izzard ; md - 



mandible; nit. mandibular 



in this class, there being pa ]p; mx, exopodite of 

 eight abdominal segments, or second maxilla : /V/ ^ pleo " 



pods; r, rostrum; s, carapace; sm, ad- 



twenty-one in all. A thin ductor muscle; /.testis; I-VI II, thoracic 



bivalve shell covers the segments -(After Claus. from Parker and 



Haswell s 1 ext-book.) 

 greater part of the body ; 



the head bears a pair of compound, stalked eves, and the 



thoracic appendages are leaflike, resembling those of the 



Fhyllopoda. The most common genus is Nebalia (Fig. 152), 



which is less than a centimeter long. 



