296 CRUSTACEA. 



FAMILY I. 



UNIPELTATA. 



IN this family the shell consists of a single shield, of an elongated quadrila- 

 teral form, usually widened and free behind, covering the head, the antenna; 

 and eyes excepted, which are placed on a common anterior articulation, and at 

 least the first segments of the body. Its anterior extremity terminates in a 

 point, or is preceded by a small plate with a similar end. All the foot-jaws, 

 the second of which are very large, and the four anterior feet, are closely 

 approximated to the mouth on two inferiorly converging lines, and have the 

 form of claws, with a single finger or mobile and flexed hook. With the ex- 

 ception of the second feet all these organs are furnished at their external 

 origin with a little pediculated vesicle. The other six feet, at the base of whose 

 third segment is a lateral appendage, are linear, terminated by a brush, and 

 simply natatory. The lateral antennae have a scale at their base, and the stem 

 of the intermediaries is composed of three filaments. The body is narrow 

 and elongated; the ocular pedicles are always short. ' 



This family is composed of but one genus, that of 



SQUILLA, Fabricius. 

 Which is now divided into the True Squillce, Gonodactytus, Coronis, &c. 



FAMILY II. 



BIPELTATA. 



IN this family we find the shell divided into two shields, the anterior of 

 which, very large and more or less oval, forms the head, and the posterior, 

 corresponding to the thorax, transverse and angular in its circumference, sup- 

 ports the foot-jaws and feet. These latter, with the exception at most of the 

 two posterior and two last foot-jaws, are slender and filiform, usually very long, 

 and accompanied by a lateral ciliated appendage. The other four foot-jaws 

 are very small and conical. The base of the lateral antennae exhibits no scale; 

 the intermediaries are terminated by two threads. The ocular pedicles are long. 

 The body is much flattened, membranous, and diaphanous; the abdomen 

 small and its posterior fin without spines. It comprises but a single genus, the 



PHYLLOSOMA, Leach, 

 Of which all the species inhabit the Atlantic Ocean and Oriental seas. 



