23 

 PLATE XII. 



LOBSTER AND CRAYFISH. 



EXTERNAL CHARACTERS 



FIG. 1. ENTIRE SPECIMEN 



,,,,, , ( Cervi cal suture between head and thorax. 



Copnalo-thorax (Or. kepnals, head: thorax, a breast- I 



i i \ \ i. r( -\ I rental spine or rostrum (L. the beak), a 



plate) covered by Carapace . . . . } 



V, prolongation in front. 



Abdo men six segments and a backward prolongation, the telson (Gr. a limit). 



C Cephalic. 

 APPENDAGES &amp;lt; Thoracic, including great claws or chelae and ambulatory limbs. 



(_ Abdominal, including the swimmerete. 

 Fio. 2. THIRD ABDOMINAL SOMITE 



f Tergum (L. the back) or dorsal portion. 

 BODY-SEGMENT -&amp;lt; Pleuron (Gr. a side). 



(_ Sternum (Gr. siernon, the breast) or ventral portion. 

 f Proto podite or basal portion (red). 

 APPENDAGES -; Exo podite or outer terminal portion (blue). 



V. Endo podite or inner terminal portion (yellow). 



FIG. 3. SIXTH ABDOMINAL SO MITE AND TELSON: a, Lobster; b, Crayfish 

 Exopodite divided transversely into two pieces. 

 Telson divided transversely in Crayfish, undivided in Lobster. 



FIGS. 4, 5. APPENDAGES OF FIRST AND SECOND ABDOMINAL SOMITES IN THE MALE 

 FIG. 4. Eudopodite, bearing a small inner process. 

 FIG. 5. Exopodite gone. 



Endopodites grooved inwardly, so that the two scooped portions brought together form a 



kind of channel. 

 FIG. 6. APPENDAGES IN ORDER 



1. Ophthalmites or eye-stalks (Gr. ophtlialmos, the eye). 



2. Anten nules with opening of auditory sac. 



3. Anten nse or feelers with opening of green gland. 

 HEAD six pair 4. Mandibles (L. mando, I chew). 



5. Maxillae, iirst pair. 



G. Maxillae, second pair with boat-shaped scaphognathite (Gr. sJcapJie, a boat ; 



(jnuthos, a jaw) for baling out and drawing in water (blue and green). 

 Maxillipedes or foot-jaws 

 7. First pair, epipodite (green) without a gill. 



3. Second pair, epipodite gill-bearing. 



THORAX eight ,, . , 



9. llnrd pair, epipodite gill-bearing. 



Chelae or pincers (Gr. chele, a claw), epipodite gill-bearing (fig. 1). 

 10. Ambulatory limb (L. ambulare, to walk), epipodite gill-bearing. 



The four pair are seen in fig. 1. 

 ABDOMEN six pair (see figs. 1-5). 

 NOTE. Seven joints of chelte and ambulatory limbs are named in order as follows (see No. 10) 



1. Coxo podito (L. coxa, the hip) or proximal joint. 



2. Basi podite . . . . ) 



3. Ischio podite (Gr. ischion, the hip) j fused to ethcr lu chela &quot; 



4. Mero podite (Gr. meros, the thigh). 



5. Carpo podite (Gr. karpos, wrist). 



6. Pro podite (Gr. pro, in front of). 



7. Dactylo podite (Gr. daktulos, a finger) or terminal joint. 

 Six joints of antenna in order (see No. 3) 



Coxo cerito (Gr. kerus, a horn). 



Basi cerite articulated with an outer llat plate, scaphocerite. 



Ischio cerite. 



Mero cerite. 



Carpo cerite. 



Pro cerite, the long many-jointed feeler. 



