NO. 5 CAMBRIAN TRILOBITES 373 



Formation and locality. — Middle Cambrian: (8w) Andrarum 

 limestone ; Paradoxides forchhammeri zone, at Andrarum, 20 miles 

 (32.2 km.) northwest of Simrishamn, Province of Christianstad, 

 Sweden. 



DOLICHOMETOPUS TONTOENSIS, new species 



Plate 51, figs. I, la-h 



This fine species I found in the upper beds of the Tonto sandstone 

 in 1882 in the form of casts in a hard sandstone. Entire specimens 

 were first collected and presented to the United States National 

 Museum in 191 1 by Mr. Niles J. Cameron, of Grand Canyon, Arizona. 

 The latter are compressed in a greenish, very fine arenaceous shale, 

 but do not retain the outer test. 



The species dififers from D. productns (pi. 53) in having a smaller 

 palpebral lobe, a median spine on each thoracic segment and the 

 anchylosed segments of the axial lobe of the pygidium, also in the 

 enlargement of the fifth thoracic segment. This character is present 

 in the 13 specimens preserving the thorax, and is not present in the 

 II associated specimens of D. productns. This species also attains a 

 larger size than any other of the genus. One entire dorsal shield has 

 a length of 97 mm., and an associated pygidium indicates that speci- 

 mens existed of no mm. in length. The next largest species, as far 

 as known, is D. bion (pi. 52, fig. 2b). 



The combination of small eye lobe, median spine on thoracic seg- 

 ments and enlarged fifth thoracic segment, suggests a reversion to 

 primitive characters in this species that might be recognized by a 

 subgeneric name if further investigation justifies it. 



At locality 74 this species is associated with the following fauna 

 in a brownish-weathering, bedded sandstone : 



Micromitra pealei (Walcott) 

 Micromitra (Paterina) crenistria (Walcott) 

 Micromitra {Paterina) superba (Walcott) 

 Micromitra (Iphidella) pannula (White) 

 Obolus zetus (Walcott) 

 Obolus (IVestonia) chuarensis (Walcott) 

 Obolus {IVestonia) euglyphus (Walcott) 

 Lingulella lineolata (Walcott) 

 Lingulella perattenuata (Whitfield) 

 Billing sella obscura Walcott 

 Alokistocare althea Walcott 



