254 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 10, 



Trinucleus tessellatus. Green, Mon. 73. 



T. Bigsbii, ib. p. 7^. 



T. Caractaci, Murch. S. S. pi. 23. fig. 1 ; Portl. Geol. Eep. pi. 1 B. 



fig. 3, 4, 5 [and also 6] ; Burm. (Ray Ed.) pi. 1. fig. 1. 

 T. elongatus, Portl. I. c. fig. 7. 

 T. latus, ib. fig. 10 to 14. 

 T. Goldfussii, Barrande*, Tril. et Sil. Syst. Bohem. p. 31 (1846). 



Spec. Char. — Outline subquadrate ; glabella obovate, not much 

 narrower below ; fringe broad, flat, produced in front and angular at 

 the sides, with about four or five rows of large puncta, not in regular 

 radii ; cheeks about equal to the glabella, rounded posteriorly, with 

 puncta beneath them ; spines as long as the entire body, directed 

 outwards, incurved at their extremities ; body and tail together as 

 long as glabella ; the first of six narrow rings ; the axis more than 

 half as broad as the pleurae ; tail very short, triangular ; the axis 

 three- or four-ribbed, and but slightly convex towards the end, where 

 the sides are a little depressed ; about three lateral furrows. 



I know four distinct varieties : — 

 a. Sternhergii, Salter; puncta close-set, four rows in front; glabella 



broad, gibbous. 

 Syn. T. ornatus, Sternberg; Barrande*. 

 /3. Caractaci ; puncta rather distant, often quincunx, three or four 



rows in front ; glabella broad, gibbous. 

 Syn. T. Caractaci, Murch. ; Burm. 



T. Goldfussii, Barrande*. 



T. tessellatus, Green, 

 y. elongatus ; puncta in sunk radii in front ; glabella and "whole axis 



elongate narrow. 

 Syn. T. elongatus, Portl. 

 ^. favus, Salter ; head transverse-rectangular, puncta in outer angles 



enlarged like honeycomb, border narrow, glabella rather narrow 



and long. 



These four varieties differ considerably in the prolongation of the 

 external angles of the head and the size and shape of the pores, but 

 in all essential characteristics they agree ; in the uniform flat, not 

 bent or divided border, the triangular few-ribbed tail, and the direc- 

 tion of the spines. 



I know of but five species : — 



T. ornatus, Sternberg : see above. 



T. seticornis, Hisinger. 



T. granulatus, Wahl. T. Lloydii, Murch. 



T.fimbriatus, Murch. 



T. radiatus, Murch. 



The latter species appears to me a good one and quite distinct. 

 Burmeister reduces it under T. ornatus, Sternb. I have carefully 

 examined the originals. 



* Barrande, in a supplement just published, has transposed these names ; but 

 this only confirms my view, as I am now sure that the Bohemian fossils in our 

 collections are the same as Sternberg's figure. — J. W, S., June 1847. 



