MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



189 



iii the figure. In our series of 88 we have 5 ossa Incce as true and typical as these a percentage 

 of 5.68. 



Fig. 33 represents the only specimen in the Salado series of what Anoutchine calls the 

 incomplete on Inccc. In this the left third of the transverse suture is persistent and, connecting 

 with the lambdoidal suture above by an almost vertical suture, separates from the rest of the 

 occipital a triangular bone which probably represents one original point of ossification. This 

 added to the complete ossa Incce gives us 6 specimens or a percentage of 6.81 of both these forms 

 combined. 



As an anomaly which is sometimes confounded with the epactal bone, though having a very 

 different embryologic origin, the quadrate bone, or os quadratum, is to be considered. Fig. 34 illus- 

 trates the only specimen in the collection which can with any propriety be classed under this 

 head, and it is neither a large nor a typical specimen. Some might be inclined to regard it as a 

 triquetral bone. One instance of this form in 88 occiputs gives us a percentage of 1.13. 



Immediately above the apex of the quadrate bone in Fig. 34 is seen an open space, which 

 was evidently once filled by a small os sagittate. 



FIG. 35. Apical bone associated with Wormian bones (No. H. 51). 



Flo. 36. Possible vestige of transverse suture (No. H. 15). 



Every separate ossicle or collection of ossicles observed at the apex of the occipital, except a 

 quadrate or an epactal bone, is placed in Virchow's class of ossa triquetra sew apicis (apical bones, 

 we shall call them), even when it lies entirely on one side of the median line or is one of the numer- 

 ous series of Wormian bones like that shown in Fig. 35. It has been found difficult or impossible 

 to draw a definite line of distinction between such and the most typical os apicis. 



In including all these forms in this class we may have exceeded the limits set for themselves 

 by other observers, and this may account for the large number (10) and the comparatively high 

 percentage (18.1) of ossa apicis which this collection furnishes. But if none but the most certain 

 examples were tabulated we would still, probably, have a higher percentage than is to be found 

 in any other race. 



There is one anomaly which we have not tabulated, namely, the vestige of the tranverse suture 

 which is sometimes seen in the neighborhood of the asterion on one or both sides and which often 

 extends but a few millimeters in the direction of the median line. This is omitted because of the 

 uncertainty attending the examination of minute examples arising from abrasions to the-outer 

 table, post-mortem marginal fissures, and other injuries common in these old and friable bones. 



In this connection I introduce Fig. 36. Here we see a peculiar punctured or honeycombed 

 appearance of the outer table in the line of the transverse suture. It seems to be a vestige of that 

 suture of unusual character confined to the outer table. It is the only specimen of its kind in the 

 Hemenway collection, but there are some similar formations in the general collection of our 

 museum. 



