23 

 PLATE XII. 



LOBSTER AND CRAYFISH. 



EXTERNAL CHARACTERS 



FIG. 1. ENTIRE SPECIMEN 



Ce'phalo-thorax (Gr. kephale, head; thorax, a breast- f *'<*L ture between head and thorax. 



plate) covered by Carapace . 1 Frontal s P me or rostrum < L ' the beak )' a 



V. prolongation in front. 



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



( Cephalic. 

 APPENDAGES < Thoracic, including great claws or chela; and ambulatory limbs. 



(_ Abdominal, including the swimmerets. 

 FIG. 2. THIRD ABDOMINAL SOMITE 



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

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



(. Sternum (Gr. stemon, the breast) or ventral portion. 

 C Proto'podite or basal portion (red). 

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



(_ 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. 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 ORDER 



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



2. Anten'nules with opening of auditory sac. 



3. Anten'nee or feelers witli opening of green gland. 



HEAD six pair 



4. Mandibles (L. mando, I chew). 



5. Maxilla?, first pair. 



6. Maxilla;, second pair with boat^shaped scaphognathite (Gr. skaplte, 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. 



THORAX oH t 3> SeC nd pair ' e ) )i P 0(nte _giU-t>earing. 



9. Third pair, epipodite gill-bearing. 



Chelae or pincers (Gr. elide, 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 chelae 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 



. . . f 



3. Ischio'podite (Gr. ischion, the hip) } fused ^ 6&cr ln chola - 



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. keras, a horn). 



l.asi'cerite articulated with an outer tlat plate, scapliocerite. 



Ischio'cerite. 



Mero'corite. 



Carpo'cerito. 



Pro'cerite, the long many-jointed feeler. 



