552 F. R. Coivper Reed — Blind Trilobifes. 



lost or destroyed, the copy may prove of great value in indicating 

 what the name was intended to cover. 



Another indirect means of protecting type-specimens would be 

 to publish catalogues of them, giving the places where they are 

 preserved. Such a list of a single group would be of great service 

 to anyone investigating it, and could be renewed from time to time 

 whenever necessary. It would be well if everyone who described 

 a species also stated where the type was deposited. In time this 

 would become the established usage, and thus greatly facilitate 

 the preparation of catalogues of types and their places of 

 preservation. 



Palgeontology has been called an exact science, but its records 

 up to the present time do not bear out this statement. If, as 

 I believe, it will yet be worthy of such a distinction, one means of 

 its advancement will be for those who represent it to select better 

 type-specimens, and preserve them more carefully. 



In all branches of Natural Science, type-specimens are the lights 

 that mark the present boundaries of knowledge. They should be, 

 therefore, not will-o'-the-wisps, leading unwary votaries of science 

 astray, but fixed beacon lights to guide and encourage investigators 

 in their search for new truth. 



VI. — Blind Tkilobites. 



By F. E. CoAVPER Reed, M.A., F.G.S. 

 {Concluded from the November Number, p. 506.) 



THE majority of fossiliferous beds in the Cambrian are of an 

 argillaceous nature, and limestones are comparatively rare, but we 

 need not here enter into a discussion as to the causes of their rarity. 

 When, however, we come to the Ordovician, we find calcareous beds 

 much developed, and since we find in them, as well as in the slates 

 and shales, these blind genera, and as far as we know not less 

 abundantly, it appears as if the physical conditions of sedimentation 

 had but little to do with the existence and perpetuation of these 

 forms. We cannot, therefore, argue that their survival was a direct 

 result of a similar physical environment ; but probably biological 

 influences which we cannot now gauge played an important part, 

 and to some extent determined their survival. Barrande, on the 

 other hand, held strongly to the opinion that the pellucidity of the 

 water in which limestones were formed led to or was associated with 

 the absence of blind trilobites, and believed that it was owing to the 

 muddy waters in which argillaceous sediment was deposited that the 

 eyeless and large-eyed trilobites were especially abundant. The 

 evidence which induced him to hold this view was obtained in 

 Bohemia, where he noticed that in the Second Fauna (which 

 jorresponds in a general way to our Ordovician) the majority of the 

 blind trilobites were found in the fine argillaceous slates of Ddl 

 and Dd 5, while the fewest occurred in those rocks (quartzites and 



