NOTES ON A COLLECTION OF SILURIAN FOSSILS — AMI. 415 



arranged, there being- some fourteen of" them visible in a length 

 of t%venty-f:wo millimetres. 



OSTRACODA. 



19. Leperditia sp. There are several specimens of a small 

 reniform species, 1.5 mm. long and 0.6 mm. broad. Rather tumid, 

 and sharply rounded at both the anterior and posterior extremity. 



VERTEBRATA. 

 PISCES. 



20. Onchijs (?) sp. — Two or possibly three spines or organs of 

 defence of one of the earliest types of vertebrates appear to be 

 present in the collection. They are tolerably well preserved, 

 and present no salient features. Cro.ss-section, .«ub-circular to 

 rhomboidal. Longitudinally, these spines are nearly straight, 

 and, being broadly and very gently curved in two directions, 

 gradually taper from the base to a more or less acute point. 



DiTnensioT}. — Length of one of these spines (which is slightly 

 imperfect), ten millimetres ; breadth, one millimetre. 



Additional note on the Fossils and the horizon they indicate. 



These fossils from Cape George seem to indicate a zone or 

 horizon which differs considerably from those of the Arisaig 

 Coast collected by Mr. Weston in 1886, and which have also been 

 examined. This is probably due to local causes 



The presence, in tolerable abundance, of shells of the genus 

 Discina is in itself quite characteristic, and a fact to be noted. 

 Besides the twenty forms described or enumerated in this paper 

 there are numerous fragments and obscure remains of fossils 

 which, although too imperfect for specific identification, never- 

 theless may serve to point out the occurrence and association of 

 the following genera. They are : Lingula, Strophomena or 

 Chonetes, Rhynchonella, Retzia, Murchisonia, Homalonotus ? 

 The presence of a number of Ludlow and Lower Helderberg 

 fossils tend to indicate an horizon well up in the SiLURlAN 

 System. 



Henry M. Ami. 



Determined at Ottawa, June, 1887. 



