MEMOIUS or THE NATIONAL ACADEMY OF SCIENCES. 



189 



ill the tigiiro. lii imr st-rirs df.ss we havi^ ."> ossa Inva- as triii- and t,vi)ical as these — a jiereeiitaKe 

 of 5.1)8. 



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

 ineompleto os Inviv. In this the left third of the transverse suture is persistent and, connectiiifi 

 with the lauibdoidal suture above liy an almost vertical sutiiic, separates from the rest of the 

 oceijiital a triangular bono which probably represt^nts one ori;;inal point of ossification. This 

 added to the complete asm Incw gives us G specimeus or a percentage of (i.81 of both these forms 

 combined. 



As an anomjily which is somotimes confounded with the epactal bone, though having a very 

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

 trates the only specimen in the eolleetion 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 bono in Fig. 34 is seen an open space, which 

 was evidently once tilled by a small on sayittale. 



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

 quadrate or an epactal bone, is ])laced in Virchow's class of ossa triquctra seu «;«cis (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 detinite 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 (16) and the comparatively high 

 percentage (18.1) of ossa apicis which this collection fimiishcs. 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 tiie direction of the median line. This is omitted because of the 

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

 table, postmortem marginal fissures, and other injuries common in these old and friable bones. 



In this connection I introduce Fig. 30. Here we see a peculiar punctured or honeycombed 

 ai)pearance 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 ontPv 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. 



