OF THE SPECIES. 89 



Tril. 41. Milne Edwards, Cmsl. iii. 327. 19. CaJ. taherculata, Murch.ü. 65G, 

 PI. 14, Fig. 4. Milne Edw. Crust, iii, 325. 14. Portlock, Bei). 284, PI. II, 

 Fig. 10. Cal. (jramdaia. Count v. Münster, Beiir. iii, 36. 3, Tab. V, Fig. 3, 

 a-d, and Cal. Icems, ibid. Fig. 4. Cal. Stokesn, Milne Edw. Crust, iii, 324. 13 

 Trinucleus {.^) leevis, Coxs-!!ii: v. Münster, i?«7/-«y(', N. 116. 1, Tab. X, Fig. 6. (?) 

 Cal. Jordani, Romer, Verst d. Harz. 37. 1. PI. XI, Fig. 4. 

 Loc. — The transition limestone of the Eifel, the Hartz, the Fichtelgebirge, Bohemia, 

 England, and North America. 



This common Trilobite is rarely well and perfectly preserved, hence the many designa- 

 tions that have been given to it. Perfect specimens with the shell are always strongly 

 granulated, as I have represented it. The granulation is most distinct on the glabella and 

 on the eyelids less so on the body-rings, and slighter everywhere on the sides, where 

 indeed it is usually altogether wanting. It is likewise not seen when the true shell is 

 absent. Brongniart, Bronn, and Murchison have figured such individuals as the normal 

 state. The axis of the tail, in specimens without a shell, has only seven rings and five ribs ; 

 two more rings and ribs are seen when the shell is present, but the two latter are very 

 slightly marked, and sometimes can scarcely be recognized. The eye, according to an 

 accurate calculation, has from 99 to i 04 lenses, many of which are frequently wanting in the 

 centre at the upper margin in some individuals, but are present in others. There are five 

 lenses at the anterior part, and two at the posterior, in the first row ; the rows then increase 

 at each side by from one to five lenses in the vertical row, upon which rows of six and 

 seven lenses alternate several times with one another ; there are usually from sixteen to 

 eighteen of such rows forming each eye. 



Remarks. — 1. Brongniart described as Cal. macrophthahna a species quite different from this, ^-ith 

 a glabella divided in lobes ; and not only has the present species, but also the C. iiiacrophthalma of 

 later authors, been described as belonging to various individuals resembling his species. The latter, 

 however, is much more common than the former or Brongniart's, and has been almost always mistaken 

 for it, although totally distinct. Honinghaus and the natm'alists of Bonn seem afterwards to have 

 repeated the error committed by Brongniart himself, and Count Stei'nberg followed in their footsteps. 

 Bronn, who at first correctly considered his Cal. Schlotheimii and C. latifrons as different, subsequently 

 returned to the error of his predecessors. Murchison and Emmerich recognized the difference of fig. 

 5 and fig. 4 of Brongniart's representation, but suffered the name erroneously given by Brongniart to 

 remain, as referring to the really undescribed figure marked 5. Milne Edwards was the first who 

 announced Brongniart's error [Crust, iii, 323, note 2), and who restored its original name to C. macronh- 

 tlialma, although the introduction of a new name for the second species was superfluous, since it had 

 already received two from Bronn. I therefore i-etain the name originally given by this careful in- 

 vestigator. 



2. In the first and second chapter, I have mentioned the species here described as /-"/;. latifrons 

 under the name of Phacops maci-oplitlialmiis, not choosing to difi'cr from the prevailing custom, and I 

 therefore called the species as it had hitherto usually been called. This, however, must not be done 

 for the future. 



2. Ph. protuberans : Lateribus tuberculi capitis subangulatis sive arcuatis ; oculis miuutis, externis. 

 Long. 2". Table III, Fig. 6. 



Ar/.— Emmr. Dissert. 19. 2. Sternb. T'er/i. d. Valerl. 31us. 1825. 77, Tab. I, Fig. 2, 

 a. c. Cal. proluh. Dalm. Pahead. 63. 9. 



Loc. — A gray limestone of the Branikberg, near Prague, (Nos 2, 18 of the Berlin 

 Museum). It is said bv Count Sternberg to occur also in Westphalia. 



12 



