68 SYSTEMATIC ARRANGEMENT 



this view is supported uot only by the relative proportions of the body which perfectly coirespond, but 

 also by the delicate nature of the covering, and the long slender spines. The remarkable prolongation 

 of the second lateral spine (uot the third, as Boeck and Count Sternberg have already correcth' shown 

 while controverting Zenker) indicates some peculiarity relative to the young age of the animal (at least 

 so far as it seems to have formed a pair of forceps with the long spine of the cephalic shield). The 

 length in this case gradually decreases as the others increase, but is still distinctly visible in individuals 

 that are half grown. I look upon Tril. minor, Boeck, as an instance of this kind. That the rings of 

 many-jointed Ciiistaceans increase in number as the animal grows, and that this number is only com- 

 plete when the animal is fully gro^v^l, is a fact too well known to the natm'alist to require proof in this 

 place, but on this suljject I would refer to my own investigation of the Phyllopoda, and the elaborate 

 and new observations of Zaddack and Joly. [Ann. des Sc. n. s. 1840 and 1842.) 



Olenus latus (Zenker /. c. Figs. W, X. Mune Edw. /. c. 441, 3) is distin9tly the same species as 

 the one above described, and is merely flatly compressed. 



2. The species Paradoxides seu Olenus Tessini (Entom. paradoxissimus, Linn. Mus. Tess. 98, Tab. 

 Ill, Pig. 1 ; Wahl. Nov. act. Ups. viii, 34, Tab I, Fig. 1 ; Brongn. Cr.f. 31, PI. IV, Fig. 1 ; Schlot. 

 Pet. Nacht, ii. 23. 1. 35. 15; Dalman, Pal. 54. 1. 73. 1. Tab. VI, Fig. 3; Boeck, May. f. Nat. I. 26; 

 Bucklaud, B. T. PI. XLVI, Fig. 8; Bronn. Leth. 1, 120, Tab. IX, Fig. 16; Quenstedt, Wieg. Arch. 

 1837, 348; Emmr. Diss. 48; Milne Edw. Cr. iii. 340, 1, PI. XXXIV, Fig. 11 ; Hising. Leth. suec. 18, 

 Tab. IV, Fig. 1) appear to me, judging from the representations and descriptions enumerated above, 

 to be scarcely different from P. bohemicus ; at least I find no certain and available difference. In 

 Linnseus's oldest figure there have been indicated at most seventeen body-rings, and the caudal shield 

 has here been distinctly represented without lateral lobes. Wahlenberg represents twenty-one such 

 rings, and twenty-two lateral lobes, the last pair of which is affixed to the caudal shield itself. 

 Dalman's figure represents a similar caudal shield, but onlj' twenty body-rings ; and both authors state 

 that they have only examined imperfect fragments, and make out no more clearly the caudal shield. 

 Brongniart copied from Wahlenberg ; Bucklaud, Bronn, Milne Edwards, and Hisinger from Dalman. 

 I consider therefore the figure given by Linna3ixs of tlie caudal shield, and Dalman's enumeration 

 of the body-rings to be correct, and I thence infer that P. Tessini is specifically identical with P. 

 bohemicus. 



3. Wahlenberg (Tab. I, Fig. 7) has figured the impression of the under side of a cephalic shield 

 (the hypostoma) as a distinct specific form, under the name of Entom. bucephalus (I. c. 37. 10, Tab. I, 

 Fig. 6). Following in his footsteps, we find Dalman {Pal. 55. 2), Schlotheim {Nacht, ii. 37), Boeck 

 {Mag.f. Nat. I, Fig. 16), Milne Edwards {Cr. iii, 341), and Hisinger (/. c. 18) expressing the same 

 view more or less doubtingly. More recently Sars {Isis 1835. 342), Quenstedt {Wieg. Arch, 1837, I. 

 349), and others, have recognized the identity of the structure with that of P. bohemicus, and M. v. 

 Buch has shown me some specimens which show the fact in a very instructive manner. I have 

 figured such an under cephalic surface in Tab. I, Fig. 7. The concentric lines there visible may be 

 observed in all under surfaces of Trilobites, and have ah-eady been alluded to by Zenker, in the work 

 already cited. Figs. C. D. 



P. spimdosus : Protuberantia capitis parabolica ; augulis scuti ceplialici dimidio corpore brevioribus, 

 trunco sedecies annulato. Long. 1". 



^,y._LiNN. Jrf. Holm. 1759, 22, Tab. I, Fig. 2. Wahl. N. a. Vps. viii, 38. Tab. I, 

 Fig. 3. Brong. Cr. /. 32, PI. IV, Figs. 2. 3. Schloth. NacMr. II. 25. 2. 36. 

 16. Dalm. P«/. 56. 2. 73. 2, Tab. V, Fig. 2. Emmr. Z»/.«*. 47. 5. Quenstedt, 

 Wiey. Arch. I. c. 349. Milne Edw. Cmsf. iii. 342. 5. Hising. Ldh. Suec. 19, 

 Tab. IV, Fig. 2. 

 I have seen only a few and not very distinct specimens of this species, but these cor- 

 responded with Walüenberg's and Brongniart's figure in tlie principal points. The cephaHc 

 shield exhil)its a glabella which is not broader anteriorly, but is gradually rounded towards 

 tliat part, with three slight impressions at each side. I counted sixteen rings in the body. 



