STOMAPODA. MTS18, OK OPOSSUM-SHRIMP. 25D 



thorax, are attached to the abdominal appendages, and hang 

 freely in the water (Fig. 576); the heart has more the form 

 and characters of the dorsal vessel of Insects ; the integuments 

 have little solidity, and are sometimes membranous and trans- 

 lucent ; and the nervous system is arranged in a less concen- 

 trated manner. All the Stomapods are marine ; and the largest 

 species are only found in tropical climates. As they are 

 inhabitants of deep waters and the open sea, rather than of the 

 shores, their habits are but little known ; but from the conform- 

 ation of some of the Order, they may be regarded with proba- 

 bility as very voracious. 



864. As connecting this Order with the last family of the 

 preceding, we may first notice the curious genus Mi/sis, or Opos- 

 sum-Shrimp ; which bears, in its general form, so strong a resem- 

 blance to the ordinary Shrimps, that it has been frequently placed 

 with them. It is distinguished, however, from the true Decapoda, 

 by the external position of its branchiae ; as well as by other cha- 

 racters. In regard to the number of 

 the feet, it holds a very interesting 

 intermediate place between the Deca- 

 pods and the ordinary Stomapods ; for 

 the last pair of feet-jaws is developed 

 into true legs, making their number 

 twelve in all; and the other two 

 pairs have much more the form of 

 ordinary legs, than in the Decapods. 

 Each of the legs has a lateral ap- 

 pendage, which is so much developed as to appear like a second 

 limb ; and thus reckoning in the feet-jaws, which also possess 

 similar appendages, we may say that the Mysis has no fewer than 

 32 legs. The common name of this curious little animal is derived 

 from the peculiar conformation, which enables it to afford a special 

 protection to the eggs. The female has a large concave scale, 

 attached to the inner division of each of the posterior legs ; and 

 these, overlapping one another, form a pouch, which is capable ot 

 being considerably distended. Into this pouch the eggs are re- 

 ceived, when they quit the ovarium ; and here they continue until 



