23 



TLATE XII. 



LOBSTER AND CRAYFISH. 



External Characters — 



Fig. 1. Entire Specimen — 



^ , , , ,, //-. 7 I 7 1 J j7 1 L ( Cervi'cal suture between head and thorax. 



Lepbalo-thorax (Gr. A<'»A!«'e, head: t/joroa;, a breast- I .^ , . ,t i i , v 



1 , s 11/. < irontal spine or rostrum (L. tue beak), a 



plate) covered by Carapace .... J , ' . „ ^ '' 



1, prolongation m front. 



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



C Cephalic. 



Appendages < Thoracic, including great claws or chelre and ambulatory limbs. 



(^Abdominal, including the swimmerets. 



Fia. 2. Third Abdominal Somite — ■ 



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



Body-Segment < Pleuron (Gr. a side). 



(^ Sternum (Gr. stenion, the breast) or ventral portion. 



C Proto'podite or basal portion (red). 



Appendages -l Exo'podite or outer terminal portion (blue). 



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



Fig. 3. Sixth Abdominal So'mite and Telson : a, Lobster ; h, Crayfish — 



Exopodite divided transversely into two pieces. 



Telson divided transversely in Crayfish, undivided in Lobster. 



Figs. 4, 3. 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. ophthahnos, 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. Maxillfe, second pair with boat-shaped scaphognathite (Gr. skaphe, a boat ; 

 ijnathos, 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. 



9. Third pair, epipodite gill-bearing. 

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



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

 The four pair are seen in fig. L 

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



2. Basi'pfdite . . . • K ,..,., , 

 o T -u- ' V, /r. -I,- IT. 1 ■ - fused together in chela, 

 o. ischio podite (Gr. ucntou, the hipj J ° 



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



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



6. Pro'podite (Gr. p)-o, in front of). 



7. Dactylo'podite (Gr. daktulos, 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 fiat plate, scaphocerite. 



Ischio'ceritc. 



Mero'corite. 



Carpo'cevite. 



Pro'cerite, the long raany-jointed feeler. 



Thorax — eight 



