File:The Quarterly journal of the Geological Society of London (13960493863).jpg

514

 ME. 
 R. 
 LYDEKKER 
 ON 
 CERTAIN 
 CHELONIAN 
 REMAINS 
 

to

 satisfy 
 myself 
 absolutely 
 that 
 this 
 form 
 is 
 generically 
 distinct 
 

from

 either 
 Hydropelta 
 of 
 the 
 Lithographic 
 Limestone 
 or 
 Ohitra- 
 

cephalus

 of 
 the 
 Wealden, 
 the 
 type 
 specimens 
 of 
 those 
 two 
 genera 
 

being

 of 
 a 
 character 
 which 
 does 
 not 
 admit 
 of 
 exact 
 comparison. 
 I 
 

shall,

 however, 
 elsewhere 
 adduce 
 certain 
 evidence 
 tending 
 to 
 show 
 

that

 Hylceochelys 
 is 
 not 
 identical 
 with 
 Ghitracephalus. 
 A 
 second 
 

species

 of 
 Hylceochelys 
 will 
 be 
 represented 
 by 
 Ohelone 
 Belli, 
 which 
 

appears

 to 
 be 
 specifically 
 distinct 
 from 
 the 
 type 
 species 
 : 
 and 
 in 
 

any

 case 
 the 
 specific 
 name 
 Belli, 
 as 
 the 
 earlier, 
 has 
 a 
 right 
 to 
 stand. 
 

The

 Chelonian 
 from 
 the 
 Kimeridgian 
 of 
 Hanover 
 described 
 by 
 

Maack

 * 
 as 
 Chelonides 
 Wittei 
 would 
 appear 
 to 
 indicate 
 a 
 form 
 more 
 

or

 less 
 closely 
 allied 
 to 
 Hylceochelys 
 ; 
 but 
 the 
 generic 
 name 
 is 
 pre- 
 

occupied

 f. 
 The 
 insufficiently 
 described 
 Plastremys, 
 Owen, 
 is 
 pro- 
 

bably

 also 
 identical 
 with 
 this 
 genus. 
 

Reverting

 to 
 the 
 forms 
 described 
 as 
 Pleurosternum, 
 it 
 is 
 evident 
 

that

 the 
 type 
 of 
 P. 
 emaryinatum, 
 Owen, 
 also 
 belongs 
 to 
 Hylceochelys, 
 

although

 the 
 other 
 examples 
 referred 
 to 
 that 
 species 
 by 
 its 
 founder 
 

are

 veritable 
 Pleurosternidae. 
 Again 
 the 
 specimen 
 from 
 the 
 Wealden 
 

of

 Germany 
 described 
 as 
 P. 
 Koeneni 
 % 
 is 
 likewise 
 referable 
 to 
 the 
 

new

 genus, 
 and 
 probably 
 belongs 
 to 
 the 
 type 
 species. 
 

The

 removal 
 of 
 these 
 three 
 species 
 from 
 Pleurosternum 
 will 
 reduce 
 

the

 four 
 species 
 assigned 
 to 
 that 
 genus 
 by 
 its 
 founder, 
 Sir 
 R. 
 Owen§, 
 

to

 two, 
 viz. 
 P. 
 continuum 
 and 
 P. 
 ovatum. 
 The 
 former 
 species 
 is 
 the 
 

first

 of 
 the 
 four 
 which 
 are 
 referred 
 to 
 the 
 genus 
 in 
 the 
 original 
 

memoir,

 and, 
 as 
 pointed 
 out 
 by 
 Prof.