OEGANISMS IN ACADIA. 159 



" Impressious which wore ouce evidently the burrows of marine annelids. Like 

 those of the ordinary Arenicolaî of onr coast they had both entrance and exit holes, so 

 that the holloAvs (and the corresponding tubercles which are the casts of these on the 

 lower surfaces of the beds) are always in pairs." 



Mr. Salter says that these hollows occur in such multitudes, and through so great an 

 extent of strata in the Longmyud (a full mile in vertical thickness) as to impress us with 

 the belief that annelid life was abundant in Cambrian times. 



We cannot see that there is any generic dilfereuce betw^een the forms described by 

 Mr. Salter under the name Arenicolites and those which Torrell calls Diplocraterion. 

 Torrell relies upon the funnel at the orifice of the tube as distingiiishing Diplocraterion 

 from Arenicolites, but siich vertical burrows could hardly exist without an enlargement 

 at the orihce, and Salter plainly depicted Arenicolites sparsus as having such a funnel. 

 Moreover Torrell admits that his Diplocraterion parallelum, majore (fig. Ab) and minore (fig. 

 bb), agree plainly with Salter's Arenicolites sparsus and didymus (figs. Aa and 5a). 



Arenicolites Lyelli, Torrell, var. minor. (PI. XI, figs. 2rt-f.) 



Twinned worm burrows having the orifices distant from each other about 30 to 50 

 mm. Diameter of the orifice, 10 to 15 mm. 



Horizon and LocaUlij. — Purplish flags of Div. \c of the Basal series on slabs wath 

 Psammichniles gigas. 



This burrow has larger and more distant openings than Arenicolites sparsus, Salter (fig. 

 4a), but not the great funnel-shaped cups of A. Lyelli, Torrell (fig. 3.) 



CHONDRITES. (PI. XI, fig. 6.) 



Numerous worm casts which by their round form and coutinuousness would come 

 under this head, are found in the flags and sandstones of the Basal series, many large ones 

 in connection with the tracks of Psammichnites, but they do not call for special descrip- 

 tion. 



Vlll.— CKL'STACEA. 



After the wealth of trilobites found in the Paradoxides beds, it seems strange to find 

 this tyi^e of crustacean so scarce in the Cambrian measures beneath. Only doubtful frag- 

 ments referable to this order have been met with. The beds of Band b, as has been 

 remarked, contain a few. In the lower part of this band were found two bivalve 

 entomostracans belonging to the genus below. 



LEPERDITIA, Rouault. 



Leperditia VENTRiCOSA, n. sp. (Plate VII, figs. 12 a-d.) 



Oval, ventricose, hinge-line short. 



Ventral valve bent inward at the hinge, and having a faint transverse ridge within, 



