228 CRUSTACEANS. 



A different specimen, of ample dimensions, which had been in my 

 possession, though always refusing to feed, from the beginning of May, 

 was then breeding unobserved. On the 21st of the month its remarkable 

 appearance struck me while inspecting the vessel. It always stood erect 

 on a piece of sponge, the body at right angles to the six hind feet. The 

 long antennae now stretched forward as usual with the species, but each 

 appeared as thick or thicker than the body itself ; and on a transient 

 glance, I thought them invested by a coating of fur ; however, this un- 

 accountable fact was easily explained by the application of a lens. A 

 numerous brood had been produced in the night, whereof the whole, 

 without exception, had seated themselves on the antennje ; yet the 

 parent neither testified impatience of their presence, nor seemed to suffer 

 any uneasiness under the burden. All were very pale or dingy white, 

 none of them extending a line. 



The young grew very rapidly. But as they continued constantly 

 affixing themselves, it certainly proved an annoyance, which was ulti- 

 mately fatal. 



This animal dwells in the deep sea : fine specimens are rare. 



Plate LXIII. 



Fig. 1. Astacilla {arcturus) longicornis, fringed apparatus. 



2. Another specimen. 



3. Anterior portion, fringed organs, a. 



4. The same enlarged, fringe, a. 



§ 4. Oniscus balthicus (Ideotea marina). — Plate LXIII. figs. 5, 6, 7, 8, 9. 



A genus of animals was constituted under the name of Oniscus by 

 the older naturalists, which perhaps engrosses the whole subjects of this 

 and the following paragraph ; they are both pelagic and littoral. Later 

 naturaUsts have incorporated the two together under the generic name 

 Ideotea. 



Length of the Oniscus balthicus from the tips of the antennae to the 

 posterior extremity twenty-one lines. The body is divided into nine 

 segments, whereof the first constitutes the head. In front are two 



