50 IMPERFECTION OF THE GEOLOGICAL RECORD 



as to the existence of unknown creatures, and thus may be as 

 important to us as the footprints of Friday to Robinson Crusoe. 

 As I have been taking Canadian examples, I may borrow one 

 here from Mr. Matthew, of St. John, New Brunswick. 



He remarks in one of his papers the manner in which the 

 Trilobites of the early Cambrian are protected with defensive 

 spines, and asks against what enemies they were intended to 

 guard. That there were enemies is further proved by the oc- 

 currence of Coprolites or masses of excrement, oval or cylin- 

 drical in form, and containing fragments of shells of Trilobites, 

 of Pteropods (Hyolithes) and of Lingula. There must there- 

 fore have been marine animals of considerable size, which 

 preyed on Trilobites. Dr. Hunt and myself have recorded 

 similar facts from the Upper Cambrian and Cambro- Silurian 

 of the Province of Quebec. No remains, however, are known 

 of animals which could have produced such coprolites, except, 

 indeed, some of the larger worms of the period, and they seem 

 scarcely large enough. In these circumstances Mr. Matthew 

 falls back on certain curious marks or scratches with which 

 large surfaces of these old rocks are covered, and which he 

 names Ctenichnites or " Comb tracks." These markings 

 seem to indicate the rapid motion of some animal touching 

 the bottom with fins or other organs ; and as we know no fishes 

 in these old rocks, the question recurs, What could it have 

 been? From the form and character of the markings Mr. 

 Matthew infers (i) That these animals lived in "schools," or 

 were social in their habits ; (2) That they had a rapid, direct, 

 darting motion; (3) That they had three or four (at least) 

 flexible arms ; (4) That these arms were furnished with hooks 

 or spines ; (5) That the creatures swam with an easy motion, 

 so that sometimes the arms of one side touched the bottom, 

 sometimes those of the other. These indications point to 

 animals allied to the modern squids or cuttlefishes, and as 

 these animals may have had no hard parts capable of pre- 



