348 Prof. T. R. Jones — On some Palceozoic Phyllopoda. 



type of the genus Pteranodon. Its principal measurements are as 

 follows : — 



Length, from extremity of sagittal crest to end of pre- 



maxillary, about 30 inches, or 760* millimetres. 



Transverse diameter of occipital condyle... 8-4 



Distance from occipital condyle to distal end of quadrate 105" 



Length of lower jaw, about 23 inches, or 585" 



Greatest depth 62" 



Depth at articulation for quadrate 23- 



The skull of Pteranodon ingens, described by the writer from the 

 same geological horizon, is about four feet in length. 



The skull of Pteranodon differs especially from that of the other 

 known Pterosauria in the following particulars : (1) the absence of 

 teeth ; (2) the absence of anterior nasal apertures distinct from the 

 antorbital openings ; (3) the presence of the elongated occipital 

 crest ; (4) the whole jaws were apparently covered with a horny 

 sheath, as in recent birds. 



Yale College, New Haven, April 2ith, 1884. 



EXPLANATION OF FIGURES on p. 347. 

 Fig. 1. Skull and lower jaw of Pteranodon longiceps, Marsh ; side view. 



„ 2. The same skull ; top view. 



,, 3. The same skull ; bottom view. 



,, 4. Lower jaw of Pteranodon longiceps ; top view. 



a. Antorbital aperture; 6. orbit; c. sagittal crest; d. angle of jaw; e. lower 

 margin of upper jaw ; e'. upper margin of lower jaw ; /. articulation of lower jaw ; 

 oc. occipital condyle ; q. quadrate bone ; s. symphysis of lower jaw. 



All the figures are one -sixth natural size. 



V. — On Some Paleozoic Phyllopoda. 

 By T. EuPERT Jones, F.R.S., and H. Woodward, LL.D., F.R.S. 



IN the Geol. Mag. Dec. II. VoL X. pp. 462-3, a Synopsis of the 

 Genera of Fossil Phyllopoda was offered as a basis for the study 

 of these interesting, though often obscure, little fossils, and some of 

 the Bivalved forms, namely, Hymenocaris, Garyocaris, and Lingidocaris, 

 were more especially noticed. See also " Report British Assoc." for 

 1882. The univalve forms (excepting Dithyrocaris) have since then 

 been carefully studied ; and the classification proposed last year is 

 found to hold good, with some slight modification, on comparison of 

 all the species of which specimens or published figures have come 

 to hand. Thus the term " flat-shield " is not strictly correct, for 

 some of these carapaces are subconical or slightly convex ; and one 

 at least (Dipterocaris) is bent like a low ridge along the back : 

 Pinnocaris is possibly really bivalved, without the triangular rostral 

 piece ; and probably Barrande's Grescentilla may be placed with 

 Pterocaris and Dipterocaris. 

 List op the Species of the Fossil Univalve Phyllopoda (except Dithyrocaris). 



I. Shield not sutured along the back. 

 1. Posterior margin entire and rounded : nuchal suture angular. 



1. DisciNOCARis, H. "Woodward, 1866. Cephalic notch broad. 



1. Browniana, H. W Shield circular.^ 



2. dubia (F. A. Roemer) ,, ,, 



3. ^a(!a (H. W.) ,, ,, 



1 In all these cases an outline outside the notch or its triangular plate is taken for 

 the real shape. 



