226 bulletin: museum of comparative zoology. 



Paradoxides spinosus W. B. Rogers, Geol. Penn., 1858, 2, p. 816, fig. 590. 

 Barrande, Bull. Soc. geol. France, 1860, 17, p. 551; Proc. Boston soc. nat. 

 hist., 1860, 7, p. 369. 



This species has often been described and is too well known to re- 

 quire any formal description here; but I wish to emphasize certain 

 features which, while now recognized, really have more importance 

 than has previously been ascribed to them. As seen by the references 

 cited above, Barrande considered P. harlam as identical with the 

 Bohemian P. spinosus. This identification was immediately con- 

 troverted by Ordway, and later writers have not accepted it; but of 

 the two really vital differences of P. harlani from P. spinosus and most 

 other species, only one has ever received attention. Ford (Amer. 

 journ. sci., 1881, ser. 3, 22, p. 250) has called attention to the fact that 

 the species of Paradoxides may be divided into two groups, in one of 

 which the second segment of the thorax is always prolonged beyond 

 the others, while in the other group the second segment is in no way 

 distinguishable from the others. To the first group belong the Bo- 

 hemian and South European species, while the Scandinavian, British, 

 and American forms belong to the second group. Paradoxides 

 spinosus has the second segment extended, while P. harlani has not. 



The second featin*e in which P. harlani differs from other species, 

 and one which makes it almost unique, is the wide, depressed brim 

 at the anterior end of the cranidium. Of the forty-six recognizable 

 species of Paradoxides whose cranidium is known, only four, Para- 

 doxides bennctti Salter, P. groomi Lapworth, P. regina INIatthew, and 

 P. harlani Green have a rimless brim (though there is a possible fifth, 

 P. hrachyrhachis Linnarsson). Of these, only two, P. harlani and 

 P. regina have a wide brim in front of the glabella. All other species 

 of Paradoxides described from adult specimens have the glabella 

 reaching nearly or quite to the anterior margin. 



Among the numerous cranidia obtained from the Paradoxides beds 

 at Braintree, there are some of the smaller ones which have a rim on 

 the front of the cranidium, and the front of the glabella almost reaches 

 the rim. These specimens have been considered by previous writers 

 to be the young of P. harlani, and it was belie^'ed that in later stages 

 of growth the anterior part of the cranidium became widened and 

 flattened. Specimens recently obtained by the WTiter from Mr. 

 Ha;y^vard's collection show that this could not have been the case, for 

 there are specimens of the broad brimmed type which are of the same 

 size or smaller than some of those showing the rim. The rimmed 



