CRUSTACEOLOGY. 



38: 



In this order the Covering is always calcai raus, and 

 is generally shield-shaped. Antenna' always four in 

 number ; the interior pair often divided. Eyes gene- 

 rally pedunculated; or placed on a footstalk ; in some 

 they are immersed in a socket. Mouth armed with 

 jaws. The mandihules two in number, bearing palpi. 

 Maxilla; six in number, placed in a longitudinal line, 

 one above the other. Four double palpi situated un- 

 der the maxilla;. Feet ten, in some fourteen, formed 

 for swimming or walking; the tarsus terminated by a 

 horny nail. Tail simple, or armed either with lamellae 

 or styles. 



Observation. The animals of this order undergo no 

 transformation ; they are for -the most part produced 

 from eggs. In the last Family, the females carry about 

 their young, until they are large and strong enough to 

 provide for themselves, 



TRIBE I. BRACHYURI. 



S'ail shorter than the body, having no caudal fin. 

 Family VII. Cancerioes. 



Shell transverse, or heart-shaped in some ; round or 

 square in others. The longitudinal very rarely exceed- 

 ing the transverse diameter. Antennae inserted into 

 excavation on the middle of the clypeus. 



I. Anterior part of the shell rounded ; posterior mar- 

 gin straight, 



* Hinder feet formed for swimming, the last joint 

 being much compressed. 



GenusXHI. Podophthalmus. Peduncle of the eyes 

 reaching the external anterior margins of the shell. 



Genus XIV. Portunus. Peduncle of the eyes 

 much shorter than the external anterior margins of the 

 shell. 



** Hinder feet, as well as all the rest, formed for 

 running, the last joint being conic. 



Genus XV. Dromia. Hinder feet placed on the 

 back. Shell very convex. 



Genus XVI. Calappa. Posterior angles of the shell 

 arched, so as to receive the hinder feet when contract- 

 ed. Hands crested. 



Genus XVII. Hepatus. The second joint of the 

 peduncle of the external double palpi triangular. 



Genus XVIII, Cancer. The second joint of the 

 peduncle of the external double palpi quadrangular. 



II. Shell more or less square. 



Genus XIX. Ocypode. Eyes with an elongated 

 footstalk inserted into the middle of the anterior mar- 

 gin of the shell. 



Genus XX. Grapsus. Eyes with a short peduncle 

 inserted in the anterior angles of the shell. Interior 

 antennae concealed by the indexed clypeus. 



Genus XXI. Plagusia. Eyes with a short pedun- 

 cle inserted at the anterior angles of the shell. Inte- 

 rior antenna? inserted into two little foveolae on the up- 

 per part of the clypeus. 



Genus XXII. Pinnotheres. Shell roundish-square. 

 The internal footstalk of the exterior double palpi one- 

 • -inted. 



Family VIII. Oxyrhynchi. 



Shell somewhat oval or triangular. The longitudi- 

 nal exceeding the transverse diameter. The anterior 

 antenna? generally exserted. 



I. All the tarsi conic. 



Genus XXIII. Leucosia. Eyes and antennae mi- 

 nute. The footstalks of the external double palpi equal. 



VOL. VII. PART M. 



Genus XXIV. Mam. Eyes distant from one an- Ci 

 other, and not small. The joints of the internal foot-- >- *' > ^*" 

 stalk of the external double palpi with two broad joints'. 

 Hinder feet not spurious- 



Genus XXV. Macropodia. Eyes distant from one 

 another. External double palpi porrected. The second 

 joint of the footstalk elongated. Hinder feet not spu- 

 rious. 



Genus XXVI. Lithodes. Eyes near each other at 

 their base. Hinder feet minute and spurious. 



Genus XXVII. Corystes. Externa! antenna? por- 

 rected as long as the body. The second joint of tlie 

 internal peduncle of the external double palpi length- 

 ened, and gradually narrowing towards the apex. 



Genus XXVIII. Mictyris. The first joint of the 

 internal footstalk of the external palpi very large. 



Genus XXIX. Douyppe. The four posterior fect- 

 plaeed on the back. 



II. The posterior feet compressed. 



* All the feet inserted in the same horizontal line. 



Genus XXX. Orythia. The two posterior feet ter- 

 minated with a swimming joint. 



Genus XXXI. Matuta. All the feet, except the 

 anterior pair, terminated by a swimming joint. 



** The four posterior feet placed over the others. 



Genus XXXII. Ranina. All the feet, except the 

 anterior pair, formed for swimming. 



TRIBE II. MACROURI. 



Tail longer than the body ; the apex furnished with 

 moveable lamella?, which are termed fins. Feet ten 

 or fourteen. 



Family IX. Pagurii. 



The caudal, lamellae, or fins, placed at a distance from 

 the middle lamella?, and not forming with it a fan-sha- 

 ped fin. 



1. Some of the feet formed for swimming, the last 

 joint being compressed. 



* Hands with one finger. 

 Genus XXXIII. Albunea. Posterior feet small 

 and filiform. The three anterior pair compressed, and 

 armed with a hook. 



Genus XXXIV. Remipes. Arms shorter than the 

 second pair of feet ; the rest formed for swimming. 

 ** Hands simple. 

 Genus XXXV. FIippa. 



2. Hands with a finger and thumb. Feet not form- 

 ed for swimming. 



Genus XXXVI. Pagurus. Tail armed with hook- 

 ed processes. 



Family X. PALiNURn. 



The lateral lamella; meeting the middle process, a»d 

 forming with it a fan-shaped fin. Peduncle of the an- 

 tenna? very long, armed at the apex with a jointed 

 seta. 



I. All the feet (arms included) terminated by a co- 

 nic tarsus. 



Genus XXXVII. Scyllarus. Exterior antennae 

 short and broad. Eyes distant. 



Genus XXXVIII. Palinurus. Exterior antenna? 

 very long and setaceous. Eyes placed on a common 

 peduncle. 



II. The two anterior feet, or arms, with a compound 

 hand. Posterior feet spurious. 



Genus XXXIX. Pohcellana. Shell roundish- 

 square. 



3-c 



