8 TRILOBITES OF GIRVAN. 



specimen is also perfect, and exhibits the ornamentation of the cheeks. The shell 

 is preserved in places attached to the cast and is of a thin delicate character. 



The second specimen likewise consists of the intaglio and natural cast of the 

 head and limb, and though the shell and ornamentation are better preserved, yet 

 the specimen has suffered somewhat from lateral compression, and is, therefore, 

 rather crushed and distorted. 



The third minute specimen, only measuring 6 mm. across, has the ornamentation 

 in beautiful preservation. 



This new species is at once distinguishable from H. flanagani, Portlock,^ by 

 its broader, more transverse form, by the curving inwards of the horns of the 

 limb, by the radiating reticulation and much finer pitting, and by the absence of the 

 intra-marginal row of large pits on the limb. 



Its affinities appear to be specially with H. spassJci, Eichwald,^ which occurs 

 in Stage C in the Baltic provinces of Russia, the characters of the limb, glabella 

 ornamentation, etc., being closely similar. In the above description the terms 

 suggested recently by Dr. Bather ^ for certain parts of the head-shield have been 

 adopted, the swollen lower part of the cheeks being designated the " cheek-roll," 

 and the smooth semi-circular areas alongside the glabella being called the " alse." 

 The term " lateral line " has also been used for the impressed concentric line 

 separating off the cheek-roll from the rest of the cheeks. 



The true homologies of the limb and cheek-roll of Hmyes are still doubtful,* 

 and it cannot be considered proved that the limb is represented in Trnnuclens or 

 Dionide. No clear evidence of a marginal suture round the edge of the limb nor 

 of a bilaminar structure of the latter, as Beecher^ stated, has been observed in 

 these Girvan specimens. 



Novak*" put all the Ordovician species of Harpes into a separate genus or sub- 

 genus which he named Harpina, on the strength of their hypostomal characters ; 

 but in the case of this and most other British species, we are unacquainted with 

 their hypostomes. Raymond"^ has recently shown that the name Harptina was pre- 

 occupied, and he has suggested the name Eoharpes for the group, and this has been 

 adopted by Ruedemann'^ and others. 



Horizon and Locality. — Balclatchie Group (Llandeilo) ; Balclatchie. 



1 Portlock, ' Greol. Rep. Londonderrv,' p. 2G8, pi. v, figs. 5 a, 5 h, 6, 7. 



2 Schmidt, ' Eev. Ostbalt. Silur. Trilob.,' pt. iv (1894), p, 66, pi. v, figs. 3—9. 



3 Bather, " Harpes hucco:' ' Rivista Ital. Paleout.,' vol. xv (1910), pp. 116—120. 



* Woods, article " Trilobita " in ' Camb. Nat. Hist.,' vol. iv (1909), pp. 226, 231, 245. 



^ Beecher, 'Amer. Journ. Sci.' [4], vol. iii (1897), p. 185. 



6 Novak, " Studieu Hypost. bi3hm. Trilob. No. 2," ' Sitzb. bohm. Gesell. Wiss.,' 1884, p. 6. 



7 Raymond, 'Amer. Journ. Sci.' [4], vol. xix (1905), p. 377. 



8 Ruedemanu, ' Bull. 162, New York State Museum' (1912), p. 116. 



