94 SHOULDER-GIRDLE AND BREAST-BONE. 



fragilis (see Plate VIII, fig. 6, i. cl.) it resembles a heart on playing-cards, but is much broader in 

 proportion to its length, and lies so that its smaller end is turned backwards. In Ophisaurus ventralis 

 it is a longer and smaller fragment which attaches itself to the anterior edge of the other piece, aud has 

 in front a long but only very shallow excavation, and on the opposite side is provided with a broad, 

 short, and rounded flat plate, which is directed backwards. In Pseudopus Pallasii it consists of a 

 slight, arched strip, moderately broad in the middle, but pointed at the ends, with its convex border 

 directed forwards, while a moderately long, small, and pointed prolongation projects from the middle 

 of its concave border. 1 In proportion to the other piece of the Sternum, the piece in question is 

 smallest in Anguis and largest in Pseudopus. Its texture is also a strong and hard bony substance, 

 in which no compound bone-cells but only quite simple bone-cavities (the so-called bone-corpuscles) are 

 present from which many branched processes or canaliculi proceed, and some of which are rounded, 

 but the greater part spindle-shaped. The Sternum is not connected closely and firmly with several 

 ribs in any of the already mentioned Saurians. Nevertheless, the larger piece of the same [pros- 

 sternum] and the first pair of ribs approximate closely, and are brought into connection by connective 

 tissue. 



I shall follow Rathke's division of the Reptiles (excluding the Ophidia proper, which have 

 no Limb-girdles), into 



1. " Sauria Annulata," or the Amphisbesnte. 



2. " Sauria Squamata Atypica," or Anguians. 



3. " Sauria Squamata Typica," or Lizards. 



4. " Sauria Loricata," or Crocodiles. 



5. " Testudinata," or Tortoises. 



Of the first group I am able to give one instance, and that the highest, viz. Chirotes this is 

 from Professor Hyrtl's preparation. 



The second group will be illustrated by four stages of Anguis fragilis, from my own 

 dissections, and a reference to these figures will help the reader to understand Rathke's description. 



My own account of Chirotes and Anguis will now follow Rathke's description ; and this will 

 give me an opportunity of commenting upon this part of his work. 



I shall afterwards give his account of these parts in the third, fourth, and fifth groups. 



1 A very accurate representation of this piece of the Sternum has been given by Miiller, loc. cit., 

 p. six, fig. 2. 



