LuEMODIPODA. 225 



They all have foiii' setaceous antcnnce supported by a tri-articulated 

 peduncle, mandibles, Avithout palpi, a vesicular body at the base of at 

 least the four pairs of feet, beginning at the second or third pair, those 

 of the head included. The body, usually filiform or linear, is com- 

 posed of eight or nine segments, including the head, and some small 

 appendages in the form of tubercles at its posterior and inferior ex- 

 tremity. The feet are terminated by a stout hook. The four anterior 

 the second of which are the largest, are always terminated by a mo- 

 nodactyle forceps or a claw. In several, the four folloAving ones are 

 shortened, less articulated, Avithout the terminal hook, or are rudi- 

 mental, and nowise adapted for the ordinary uses of similar parts. 



The females carry their ova under the second and third segmerjts 

 of the body in a pouch formed of approximated scales. 



They are all marine Crustacea. M. Savigny considers them as 

 allied to the Pycnogonides, and constituting with the latter tlie tran- 

 sition from the Crustacea to the Arachnides. In the first edition of 

 this work they formed the first section of tlie Isopoda, that of the Cis- 

 tibranchiata. 



We may vuaite them in a single genus which, by the law of priority 

 should be called the 



Cyamus, Lat. 



Some — the Filiforma, Lat. — have a long and veiy slender or 

 linear body with longitudinal segments ; feet equally slender and 

 elongated, and the stem of the antennae composed of several small 

 joints. 



Tliey are found among marine plants, walk like the caterpillar 

 termed the Geometra, sometimes rapidly revolving in a circle, or 

 turning up their body, during which time the antennse are vibrating. 

 \yhile swimming, the extremities of their body are curved. 



Leptojiera, Lat. — Proto, Leach. 



Fourteen feet, including the two annexed to the head, all complete 

 and in a continuous series. 



Here, as in our L-.ttomera proper — Gammariis pedatus. Mull., 

 Zool. Dan., CI, 1, 2 — all the feet, the two anterior excepted, have a 

 vesicular body at their base. 



There, as in the Proto, Leach — Cancer pedatus, Montag., Trans. 

 Lin. Soc, II, 6; Encyclop. Method., Atl. d'Hist. Nat, CCCXXXVI, 

 38 — those appendages are only proper to the second, and four fol- 

 lowing feet *. 



* We should also refer to the Leptomerae, the Squilla ventricosa, Mull., Zool. 

 Dan., LVI, l — 3 ; Herbst., XXXVI, ii : — the Cancer linearis, L., is perhaps a con- 

 gener. He describes it as having si.x feet, but does not include the head. 



VOL, III. Q 



