BRITISH FOSSILS. 



5 



The foregoing Species belongs to Section 2. — Agnostus proper. 

 [Agnostus pisifoemis, Linn. 



I subjoin a description of the Swedish species, as it is necessary 

 to show in what respects this long-known primordial species differs 

 from the preceding, and also from the A, McCoyii, under which 

 name I have designated the species common in the Llandeilo flags 

 of Britain, and which was formerly published in the Silurian 

 System as A. pisiformis. 



Synonyms. Ent07nosfracites paradoxus and E. jnsifonnis^ Linn,, Iter 

 Scan. 122 ; Syst. Naturse, ed. 16, vol. iii. 160 ; E. pisiformis, Wahl. ; 

 Agnostus pisiformis^ Brongn. (1822), Crust. Foss. pi. 4, fig. 4 ; Angelin, 

 (1852), Pal. Siiec. t. 6, fig. 7 {A. planicanda, ib. t. 6, fig. 9, variety). 



Diagnosis. A. elongatus, 6 liiieas longus, valde trilobus, capite et 

 pygidio ovali-truncatis, IcBvibus. Glabella longiconica, in duas partes, 

 anticam trigonam parvnm, posticam oblongam, divisa. Cauda axi magno, 

 longo, lobato, apice obtuso ; marginibus angustis brevidentatis. Locality. 

 — Lingula flags of Siveden. 



Comparing, then, the Swedish figure with that given of our next 

 species, it will be seen that the general shape of A. pisiformis is 

 much longer, and the glabella narrower and more pointed ; its 

 upper lobe, instead of being larger than the lower, is much smaller, 

 and from its apex a longitudinal furrow runs to the front margin. 

 In these respects it agrees with our A. princeps, as before said, but 

 differs. from the Llandeilo fossil A. McCoyii. 



There are also considerable differences in the caudal shield, as 

 will be seen by referring to the following figures.] 



Section 1. — Condylopyge. 



AGNOSTUS MACCOTII. 



Plate I. Figs. 6, 7. 



Diagnosis. A. oblongus, depressus, capite pygidioque rotundatis, et 

 ad thoracem contractis. Glabella oblonga, ajitice vix incrassata^ in duas 

 partes sub-cequales, posticam circularem, anticam lunatam, sulco curvo 

 divisa. Limbus undique cequalis, lineis impressis radiatis scepe notatus, 

 margine angusto. Cauda capiti simillimay sed axi clavato brevi, lobo 

 terminali majori semielliptico, mediano transverso hrevituberculato, lobis 

 anticis prominulis. Margo distinctus, brevidentatus. 



Synonyms. A. pisiformis? Murch. (1837), Sil. Syst. pi. 25, fig. G 

 (fig. 4 in text), not of Brongniart ; Diplorrhina triplicata, McCoy 



11 A 3 



