Professor J. W. Judd—Wm. Smith's M8. Maps. 439 



" The facial region of the skull is narrow and elongate. On the 

 outer surface of the maxillary, just above the antorbital foramen, 

 there is a deep depression, which probably contained a gland. The 

 usual ruminant fossa in front of the orbit appears to be wanting. 

 The orbit is large, and completely closed behind by a strong bar 

 of bone. 



" The dentition preserved is selenodont and brachyodont, with 

 only three premolars and three molars.^ The first premolar is 

 much compressed transversely, and has but a slight inner lobe. 

 The second premolar is triangular in outline, the inner lobe being 

 much more developed. The last premolar has this lobe expanded 

 into a strong cusp, and the crown thus becomes broader than long. 

 The true molars have two inner cusps, each with a basal ridge. 

 The outer crescents have a median vertical ridge. The enamel of 

 the molar series is more or less rugose. There was a wide diastema 

 in front of the premolars. 



" The posterior nares are situated far forward, the anterior border 

 being .opposite to the posterior cusp of the second true molar. The 

 glenoid facet is large and convex, but the postglenoid process is 

 quite small. The paroccipital processes were well developed, but 

 there were apparently no auditory buUee." 



A number of other female skulls, some of them in excellent 

 preservation, have since been obtained from the same region in 

 which the type was found, and a study of these makes clear the 

 main points of their structure. It is not quite certain to which of 

 the three species of Frotoceras now known some of these skulls 

 should be referred, but further investigation will doubtless determine 

 this point, as the present material in the Yale Museum is apparently 

 sufficient for this purpose. 



All the known remains of Frotoceras are from the Upper Miocene 

 of South Dakota. The horizon, which is a definite one, has been 

 appropriately called by Dr. Wortman the Frotoceras beds. They 

 appear to be identical with the series in Oi'egon, which the writer 

 had previously named the MioMppus beds, as that genus and several 

 others are common to both regions. 



EXPLANATION OF PLATE XIX. 

 Skull of the male of Frotoceras celer, Marsh ; oblique side view. Three-fourths 

 natural size. Miocene: South Dakota, U.S.A. 



II. — William Smith's Manuscript Maps. 



By Professor J. W. Judd, C.B., LL.D., F.R.S., F.G.S., etc. 



IT is well known to all students of the history of geology that, 

 although the date of publication of William Smith's " Map of 

 the Strata of England and Wales " was the year 1815, yet even before 

 the commencement of the present century the " Father of English 

 Geology " had not only established the principle that strata can 

 be identified by their organic remains, but had actually applied that 



1 More perfect specimens since discovered prove that there were four premolars, 

 the first being absent in the type. 



