Vol. 5] 



Merriam. — Osteology of Nectosaurus. 



219 



absent. The length of the jaw from the anterior end of the clen- 

 tary to the middle of the cotylus is 85 mm. The height of the 

 mandible near the middle is a little less than 13 mm. 



The pterygoid is represented by several specimens which have 

 been so weathered as to show the lateral and inferior aspects of 

 this bone. A lateral view of No. 10770 shows the high superior 

 wing, which is about as prominent as in Thalattosaurus, and is 

 similarly sculptured. In specimen 10817 (pi. 17, fig. 3) the 

 palatal side of a very small individual is exposed. It is not es- 

 sentially different from that of the pterygoid of the type specimen 

 of Thalattosaurus. The dentigerous area shows three or more 

 longitudinal rows of distinct pits in a few of which the broken 

 fangs of the teeth remain. The edentulous area next the base of 

 the superior wing has about the same form as in Thalattosaurus 

 alexandrae. 



Another and somewhat larger pterygoid, No. 10626 (pi. 17, 

 fig. 2) may represent Nectosaurus or one of the smaller species of 

 Thalattosaurus. The well exposed dentigerous area shows not 

 less than three longitudinal rows of teeth, of which one has con- 

 tained at least seven teeth. The crowns are all circular in cross- 

 section, and the two or three which are complete are slender acum- 

 inate. The bases of several of the larger teeth are distinctly seen 

 to be anchylosed to the bone. 



Arches and Limbs. 



The scapula of Nectosaurus (pi. 18, fig. 2), which has not been 

 known before, has a form closely resembling that of Thalatto- 

 saurus shastensis, from which it differs mainly in its somewhat 

 narrower distal blade. 



A number of small, slender limb bones, principally represent- 

 ing the propodial segments of the limbs, have been found with 

 other material referred to Nectosaurus. Several of these are 

 nearly complete and show the shaft to be more slender than that 

 of Tltalattosaurus shastensis. The middle region of the shaft is 

 nearly round in cross-section. The proximal end is slightly ex- 

 panded. The distal extremity is considerably broadened and flat- 

 tened (No. 10800, pi. 18, fig. 1). It is uncertain whether these 

 elements represent the humerus or the femur, but in one or two 



