84 Dr. W. Baird on British Entomostraca. 



distance from the eye, much smaller than it, which was con- 

 sidered by Miiller as a second organ of sight, and from which 

 he has given the name to the genus*, and the shape of the 

 head and beak. The shell, or covering which incloses the body, 

 does not consist of two distinct and separate valves, but is 

 open only on the anterior margin, and for a portion of the 

 posterior extremity. The part which we may call the head is 

 harder than the other portion of the shell, and is prolonged, in 

 most of the species, into a sharp and very distinct beak. Be- 

 longing to it we find, besides this beak, the eye with its ac- 

 companying black spot, the two antennae, the rami, brain, 

 mouth, and part of the digestive canal. The eye, as in the 

 Daphnice, is a spherical body contained in a somewhat funnel- 

 shaped tube, having a semirotatory motion, and consisting of 

 a series of crystalline bodies, in the lamellatus^ being about 

 twenty in number (PL II. f. 2.). The black spot which Miiller 

 considers as a second eye, is situate before and at a little dis- 

 tance from the real eye, generally near the end of the beak, 

 almost at the extremity of the body of the animal, and near 

 the root of the antennae, It is much smaller than the eye, has 

 no communication with it, and is immoveable. It is not com- 

 posed of crystallines, and its situation is not exactly the same 

 in all the species. Jurine says he has only examined it in small 

 individuals, and that in consequence he has not been able to 

 discover its use. He does not appear to have met with the 

 larger species of the genus, the lamellatus, in which I have 

 examined this spot, but without being able to discover any use 

 to which it is applied. I quite agree with him however in con - 

 sidering it not to be an organ of vision. Straus considers the 

 upper larger spot alone deserving the name of eye, and that 

 this small black spot is similar to the one which exists in the 

 Daphnice, adjacent to the brain ; the relative situation too of 

 which is nearly the same as this black spot in the Lyncei J. 

 As I have said above, we find it in the young before birth ex- 

 actly as in the adult. The antenna are two in number, and 

 are placed near the extremity of the beak, projecting from its 

 under surface. Each consists of a solid body of a somewhat 

 conical shape and slightly curved, which terminates in six 

 short spines, each of which again gives out a fine seta or 

 bristle (PL II. f. 3.). They are not possessed of much motion. 

 The rami § or arms are situate on each side of the base of the 

 head, rather lower than in the Daphniaz, and consist, as in them, 



* "Nomen Lyncei in 'Zool. Dan. Prodrom,'ex punctis binis ocellaribus, 

 quae organa visus absque dubio sunt, indici." — Entomost. p. 67. 

 •f* Eurycercus lamellatus, nob. 

 X Mem. Mus. Hist. Nat. torn. vi. p. 15.3. 

 § Antennae of Miiller, &c. 



