No. 3.] ZOOLOGY AND BOTANY. 359 



like it has been made known amoncr the livinGr shells. Now 

 among the few specimens dredged on this occasion in 500 fathoms 

 depth, off the mouth of the Rio Doce, there was one living speci- 

 men of the same type as the Pecten paradoxus, showing particu- 

 larly, and very distinctly, the prominent radiating ribs rising on 

 the inner surface of the shallow valve to which the fossil is in- 

 debted for its specific name. Like the fossil, the living species is 

 of small dimensions, measuring hardly two-thirds of an inch. I 

 hope I may be able to dissect the animal at some future time, 

 and work out the anatomical character of this exceptional type. 

 With it a few other shells, already known to us, from deep waters, 

 were also found ; among them, two beautiful species of Pleuroto- 

 ma, identical with species found in Florida, off Barbados. 



In my first letter to you concerning deep-sea dredging, you 

 may have noticed the paragraph concerning Crustacea, in which 

 it is stated that among these animals we may expect "genera re- 

 minding us of some Amphipods and Isopods aping still more 

 closely the Trilobites than Scrolls. " A specimen answering fully 

 to this statement has actually been dredged in 45 fathoms, about 

 40 miles east of Cape Frio. It is a most curious animal. At first 

 sight it looks like an ordinary Isopod, with a broad, short, flat 

 body. Tested by the characters assigned to the leading groups of 

 Crustacea, whether we follow Milne Edwards, or Dana's classifica- 

 tion, it can, however, be referred to no one of their orders or 

 families. As I have not the works of the authors before me, I 

 shall have to verify more carefully these statements hereafter, 

 but I believe I can trust my first inspection. The general ap- 

 pearance of my new crustacean is very like that of Scrolls, with 

 this marked difference, however, that the thoracic rings are 

 much more numerous and the abdomen or pygidium is much 

 smaller. It cannot be referred to the Podopthalmians of Milne 

 Edwards (which corresponds to the Decapods of Dana) because 

 it has neither the structure of the mouth, nor the gills, nor the 

 legs, nor the pedunculated eyes of this highest type of the Crusta- 

 cea ; nor can it be referred to the Tetradecapods of Dana (which 

 embrace Milne Edwards's Amphipods and Isopods), because it 

 has more than seven pairs of thoracic limbs ; it cannot be referred 

 to the Entomostraca, because the thoracic are all provided with 

 locomotive appendages of the same kind. But it has a very strik- 

 ing resemblance to the Trilobites ; it is in fact, like the latter, one 

 of those types, combining the characteristic structural features of 



