DIFFUSION OP THE CAMBRIAN FAUNAS. 11 



with again ou the slopes of the Adirondack Mountains in Northern New York. Here Mr. 

 Walcott recognized two species, one identical with a species in Wisconsin. 



The geuus is found again at Pt. Levis opposite Quebec, whence and from neighbour- 

 ing places Mr. Billings described fourteen species, of which, however, only three or foi;r 

 are properly referable to this genus.' 



Mr. Walcott described or quoted ten Cambrian species of Dicellocephalus from the 

 country west of the Eocky Mountains, but of these only three or four are fairly within 

 the genus or sufficiently perfect for purposes of comparison.' These species are no nearer 

 the original types than those described by Billings from the limestone conglomerate of 

 Pt. Levis. 



On the other side of the Atlantic the genus reappears in Wales where there were 

 several species,'^ only one of which {D. furca) is entitled to rank as an unquestionable 

 Dicellocephalus. 



In Scandinavia two species have been recognized, one (Z). dicrœura) has apygidium so 

 like that oï D. furca that it must be closely related ; the other [D. serrata) is referred to this 

 genus on account of the fan-shaped, serrate pygidium, but as the head is not known the 

 reference is open to question. 



We have thus traced the genus Dicellocephalus across the Atlantic from America to 

 Europe, let us now note what companions it had on the two sides of this ocean. Prof. 



^ D. pkmifroiis, D. Oirini, D. majalojix, ami (moro doubtfully) D. Belli. The fos.sns of this genus occur in 

 boulders in the limestone baud No. 1 of the Levis shales opposite Quebec. Of the species occurring here it may be 

 said that D. Dcvinrl by the form of the glabella and the attitude of the glabellar furrows is a Conocephalites; the 

 pygidium figured is only provisionally referred to this species. D. Hisivgeri is also a Conocephalites. D- affinis 

 compared to D. Oiceni by some error is too obscure to be considered. D. Sefostrii appears to be near Walcott's genu.s 

 Oryctocephalus, but is not a Dicellocephalus. D. nelcctus is said to resemble D. Senostriit. D. Minaisijuoi is founded 

 on a pygidium like that of D. magiiilicus. D. magnificux has not the glabella and scarcely the pygidinm of a 

 Dicellocephalus. Dpavper, said to resemble D. iSesoslris, has not the form of glabella proper to a Dicellocephalus. 

 D. phinifrons and D. Oven! more nearly represent the typical forms of Wisconsin, and D. Belli may also be in- 

 cluded, though the form of the glabella is not characteristic. D. megalopx approaches the typical examples of the 

 genus by its glaljellar furrows and dorsal suture. 1>. criHatus has a smooth glaliella and is not very closely related 

 to the typical species. J5. (.O coroo; shows some remarkable points of resemblance to Parabolina spinulosa. The 

 pygidium has the same number of rings in the axis, and the lateral costa are similar in curve and furrows. Except 

 that the glabella is more conical and is shortened it agrees with that of P. xpinulom. A wide margin in front of 

 the glabella is represented in the cut but not described in the text. A mark at each side of the head represents 

 in its position the eyelobe of Parabolina. 



- D. Richmondenxis, D. Mnrica, D. lolc and D. (f) angustifromi. Of the western species described by Mr. Walcott 

 (Palfeontol. Eureka Distr. p. 42, etc.) D. Richmond ensis is a fair representative of the genus. D. Marica also as re- 

 gards the glabella, but not as regards the dor-sal suture. D. lole is a form resembling D. Belli of the Levis beds, which 

 is scarcely typical. D. {') unynstifrons is imperfect but stands in about the same relation to the types as D. Belli. 

 Compare it with Hall's ConoccphcdiU:» Eos. D. nasiihis neither by its suture nor by its glabella, comes within Hall's 

 conception of the genus. D. hilobatus, H. & W., was founded on a pygidium. D. Osceola, Hall, already described from 

 Wisconsin. D. (f) i/uad deeps, H. & W., this is more like a Barrandia than a Dicellocephalus. D. (f) e.e/iansw:, this 

 also can hardly be included in the genus. D. Hagillifer, H. & W., not described in Mr. Walcott's work. D.Jliialis, 

 this Silurian species recalls the Z>. cora.i of Billings, but the deviation from Parabolina .ipiinUosa is more pro- 

 nounced. D. inexpeclans, this species also Silurian, represents the features of tlie genus except that the glabellar 

 furrows are not fully transverse and the first one does not go across. For so late a species it is remarkably near 

 the type. 



' Memoirs Geol. Surv. G.B., vol. III., p. 497. JJ. furca. Salt., is a typical form allied to D. Minnesotengis and D. 

 Prpinensis. D. Celticus is founded on a pygidium. D. diKoidalis, Salt., has all the characters of the genus except the 

 transverse furrows. Conocoryphe abdita has much the same form. 



