23 

 PLATE XII. 



LOBSTER AND CRAYFISH. 



EXTERNAL CHAEACTEES 



FIG. 1. ENTIEE SPECIMEN 



,-,,,,,, /r , , . , , , ,, , , ( Cervi'cal suture between head and thorax. 



Co phalo-thorax (Gr. kephale. head ; thorax, a breast- I 



i , \ \ , A < Frontal spine or rostrum (L. the beak), a 



plate) covered by Carapace . J " 



V prolongation in iront. 



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



C Cephalic. 

 APPENDAGES -J Thoracic, including great claws or chelse and ambulatory limbs. 



V. Abdominal, including the swimmerets. 

 FIG. 2. THIED ABDOMINAL SOMITE 



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

 BODY-SEGMENT -j Pleuron (Gr. a side). 



t Sternum (Gr. sternon, the breast) or ventral portion. 

 f Proto'podite or basal portion (red). 

 APPENDAGES J. Exo'podite or outer terminal portion (blue). 



(, Endo'podite or inner terminal portion (yellow). 



Fio. 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 FIEST AND SECOND ABDOMINAL SOMITES IN THE MALE 

 FIG. 4. Endopodite, 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 OEDEE 



1. Ophthalmites or eye-stalks (Gr. ophthalmos, 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, first pair. 



6. Maxillae, second pair with boat-shaped scaphognathite (Gr. slcaphe, a boat j 



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

 Maxillipedes or foot-jaws 



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



8. Second pair, epipodite gill-bearing. 



-eight 9 Third pai]-j epipodite 



Chelse 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 chelse and ambulatory limbs are named in order as follows (see No. 10) 



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



2. Basi'podite . . . . \ . 



o T I,-' Ti /n ! it. i \ c fused together in chela. 



3. Ischio podite (Gr. ischwn, the hip) ) 



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



5. Carpo'podite (Gr. Jcarpos, wrist). 



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



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

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



Coxo'cerite (Gr. keras, a horn). 



Basi'cerite articulated with an outer llat plate, scaphocerite. 



Ischio'cerite. 



Mero'cerite. 



Carpo'cerite. 



Pro'cerite, the long many-jointed feeler. 



