ZOOLOGY. 809 



bone is fixed aud the ribs are two-headed ; the pre-coracoid bone is 

 present aud the coracoid bone is of reduced size and is free at the ex- 

 tremity; the vertebral centra are deeply biconcave, and the pubis is 

 entirely anterior to the ischium, and is united with it without interven- 

 ing: obturator foramen. The order tb us distinguished has been mostly 

 studied in remains found in the Permian deposits of Texas, but like 

 forms have been found at the Cape of Good Hope as well as in Per- 

 mian deposits in Europe. Some of'the representatives were of the order 

 long ago exhumed in Cape Colony aud were described by Professor 

 Owen under the name Therodontia. The great English naturalist 

 noticed the similarity in the teeth as well as in the bone of the leg, es- 

 pecially of the anterior leg of the reptiles to corresponding parts of mam- 

 mals, but the full significance of the similarities was not appreciated 

 until subjected to examination by Professor Cope. Professor Cope di- 

 vides the theromorphous reptiles into two divisions : first, the Anoino- 

 dontia, where there are several sacral vertebrae, and the vertebrae are 

 not notochordal ; and second, the Pelycosauria, where the vertebrae are 

 notochordnl, and there are only two or three sacral vertebrae. It is the 

 latter suborder that is most noteworthy. Its species are*so far only 

 known from beds of the Permian epoch. They were moreover the only 

 known reptiles of that epoch, for it is not until the following or Triassic 

 period that the orders which characterize Mesozoic time made their ap- 

 pearance. 



Professor Cope has given details on the " structure of the columella 

 auris in Clepsydrops lei)toupbalus," on the '• structure of the quadrate 

 bone in the genus Clepsydrops," and on " the articulation of the ribs in 

 Embolophorus," and on " the posterior foot in Pelycosauria." The con- 

 sideration of the characteristics revealed by this examination has led 

 Professor Coi)e to the following conclusions : 



(1) " The relations and number of the bones of the posterior foot are 

 those of the Mammalia much more than those of the Eei)tilia." 



(2) " The relations of the astragalus and calcaneum to each other aie 

 as in the Monotreme Platypus anatinus," or rather Ornithorhynchus 

 anatinus. 



(3) " The articulation of the fibula with both calcaneum and astraga- 

 lus is as in the Monotreme order of mammals." 



(4) "The separate articulation of the anterior part of the astragalus 

 with the tibia is as in the same order." 



(5) "The presence of a facet for an articulation of a spur is as in the 

 same order." 



((>) "The posterior- exterior direction of the digits is as in the known 

 species of the Monotremata." 



Professor Cope concludes from this survey that tliere are good "rea- 

 sons for believing that the mammalfa are the descendants of the Pely- 

 cosauria." {Proc. Am. Assoc. Adv. Sc, v. 3."J, pp. 471-482.) 



