BRANCHIPUS. CRUSTACEA. 187 



of feet ; head not distinct from the body, and covered by a 

 membranous shield, formed of two adhering plates, carinated 

 in the middle and notched posteriorly ; antennae very short, 

 inserted near the mandibles ; tail terminated by two long se- 

 taceous and multiarticulate filaments. 



The animals of this genus are remarkable for their almost instantaneous develope- 

 ment in great numbers in marshes formed by a heavy fall of rain. Their ova seem 

 to have the faculty of being preserved for a long time even in dry places without 

 perishing. 



A. cancriformis, Cuv. (Limulut palustris, Mull.) Posterior notch 

 of the shell very large ; dorsal carina prolonged and pointed. 1^ 

 inch long. Inhabits France, &c. Desrn. Crust. 360. 



FAMILY II. CERATOPHTHALMA. 

 Destitute of shell ; eyes on peduncles. 

 Gen. 3. BJIANCHIPUS, Lam. Cancer, Lin. 

 Body elongated, almost filiform, and very soft ; head distinct, 

 with filiform straight flexible antennae, to the number of two 

 or four ; two reticulated eyes ; two kind of horns in front, 

 largest in the males ; feet proper for swimming, and of equal 

 length ; tail of from six to nine segments, the last with two 

 elongated leaflets. 



B. stagnalis, Lat. Horns of the male horizontal ; fins of the tail 

 broad ; four antennae ; ova of the female blue, in an oval bag un- 

 der the tail. Herbst, pi. 35, fig. 3-10. 



Gen. 4. ARTEMIA, Leach. Cancer, Lin. 

 Body oval, with the head not distinct ; two short subulate an- 

 tennae ; tail long, pointed ; ten pairs of lamellar ciliated feet 

 or fins, terminated by a seta. 



A. salina, Leach. Very small. Common in the salt marshes at 

 Lymington. Desm. Crust. 393. 



ORDER VIII. XYPHOSURA. 



Body divided into two parts ; no syphon ; base of the feet, the 

 two last excepted, rough with small spines, and serving as 

 jaws ; shell hard, in two portions, with two longitudinal fur- 

 rows above, and covering all the body ; body terminated by 

 a hard ensiform portion. 



The animals of this order have the body divided into two portions, of which the 

 anterior forms the cephalo-thorax, and the posterior the post-abdomen. The first 

 is covered by a lunated shield, bearing two distant eyes ; two antennae below in the 

 form of didactyle or monodactyle claws, according to the sexes ; and six pairs of di- 

 dactyle feet, of which the last two united form a large leaflet bearing the sexual or- 

 gans. The second portion of the body is covered by a triangular shield, notched 



