PEOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 399 



Taken as a whole we could hardly look for a better example of a rudi- 

 meutary apparatus throughout, even to its minor details. In Gerrliono- 

 tus, all of the points that are so feebly developed in Opheosaurus have 

 been carried to a still higher point, and one approaching the true Lacer- 

 tilian type, and although in this lizard the anterior and posterior limbs 

 are present, they are weaker than in other forms, such as the Iguanidw. 

 In Gcrrhonotns tbe clavicles meet mcsiad, and the coracoids articulate 

 with elongated facets upon a semi-osseous sternum, that has inserted 

 along its sides the hesmapophyses that articulate above with the dorsal 

 ribs. Passiug next to the examination of the pelvis, we find that 

 although some parts have been more or less suppressed or have almost 

 passed beyond recognition, we still find a rudimentary femur present. 

 The fifty-seventh vertebra has suspended from its diapophyses, and 

 articulating freely with their extremities, two spoon-shaped bones, one 

 on either side; these do not meet in the median line, but are sei^arated 

 by a space of several millimeters. Tbe dilated extremity of each is below, 

 and from the middle point on the outside surface, rotating in a diminu- 

 tive acetabulum, we find the rudimentary femur, represented hj a 

 minute cylinder of bone, rouuded at both extremities. A 

 faint sutural line passing through this coty- 

 : loid-cavity indicates the division between the 

 ilium above and the puboischium below. Pro- 

 fessor Mivart found this condition in some of 

 ^'j-^- the forms he examined, and he tells us in his t.^.s 



Lessons in Elementary Anatomj^, page 195, that "•confining ourselves, 

 therefore, for purposes of comparison, to Mammals, Sauropsida, and 

 Batrachians, we find the femur uuder a certain aspect more constantly 

 present than the humerus. For although it is often absent when the 

 humerus is present (as in forms like Siren, which have j)ectoral limbs 

 but no i)elvic ones), yet it is sometiuies present in a more or less 

 rudimentary condition when no representative of the foot coexists with 

 it. Such is the case, e. g , in some whales (as the Greenland whale) 

 amongst mammals, and certain snakes, e. g., Boa, and certain lizards, 

 e. g., Liaiis, amongst the reptiles." 



In Gerrhonotus all three of the i^ehic bones go to form the acetabulum, 

 the pubic elements curving far anteriorly as delicate osseous columns 

 to meet, mesiad, in a common cartilaginous articulation. The arch is 

 suspended in a lilce manner from the transverse processes of a vertebra. 

 Though a little foreign to our subject, it will be of interest to many 

 to know something of th(; character of food of this lizard, and in this 

 Professor Riley hits kindly assisted me, and sends the following diagno- 

 sis of a stomach that I sent him : 



"The contents of stomach of Opheosaurus ventralis consists almost en- 

 tirely of fragments of a tolerably common spider, Lycosa ruricola Hentz, 

 with a single small black seed and seed-pod of some plant, not determ- 

 inable on account of condition." 



