Ortmann — Linuparus atavus. 293 



their closer position to the median line, the horns approach 

 also the condition seen in Linuparus.* 



There is no doubt that we are to place the fossil form in the 

 genus Linuparus, and although the frontal horns form in some 

 degree a connection with Palinurus, there are a couple of other 

 characters of minor importance exhibited by our fossil which 

 occur only in the Japanese Linuparus trigonus, as will be 

 pointed out in the following detailed description of the new 

 fossil, which I propose to name 



Linuparus atavus, spec, no v. 



The two specimens of the Princeton Museum, both males, 

 were collected by Mr. H. F. Wells in the Niobrara group 

 (Upper Cretaceous) at the head of Cotton-Wood Creek, Mead 

 Co., South Dakota. They were broken into numerous pieces, 

 but have been put together again very skilfully by Mr. Gidley. 

 The matrix being extremely hard, it was deemed dangerous to 

 try to work out some parts of the body more completely ; thus 

 some parts in either specimen are still imbedded in the matrix : 

 but luckily the specimens supplement each other in an admira- 

 ble manner, so as to leave only a few details of minor import- 

 ance unknown. See figures 1-4, p. 297. 



Measurements. 



Of larger specimen (a). 



From anterior frontal margin to hinder lateral corner of 



carapace -- _---- 79 mm 



Length of 4 posterior abdominal segments + telson (hinder 



part of the latter imbedded in the matrix) 77 



Length of the three free basal joints of the antennas (outer 



margin) -. 39 



Breadth of frontal margin 38 



Distance between the frontal horns, _ - - 8 



Breadth of carapace, posterior end . . _ - - 36 



Of smaller specimen (b). 



Length of carapace — 60 mm 



Length of 4 anterior abdominal segments 31 



Allowing, in the larger specimen, for the first two abdom- 

 inal segments one and a half of the length of the third seg- 

 ment (14 mm ), the approximate total length of the body would 



be 177 mm . 



* This intermediate shape of the frontal horns settles the question, whether the 

 triangular frontal processes of Linuparus are a bilobed rostrum (as de Haan be- 

 lieves) or the homologues of the frontal horns found in other genera of Palinuridae. 

 They are frontal horns. 



