384 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



DESCRIPTION OF PLATE 25 



PAGE 



Elliptoccphala asapliuidcs Emmons (See pis. 24 and 44) 269 



Fig. I. A young stage (Paraprotaspis) in which the pygidium is out- 

 lined and the genal and intergenal spines united. X 16. 



2. Cephalon with the genal and intergenal spines slightly separated. 



Xio. 



3. Cephalon with the genal and intergenal spines widely separated 



but with the genal angles carried slightly forward. X 10. See 

 figs. 3 and 4, pi. 30. 



4. Cephalon with transverse posterior margin and normal form 



of genal spines. X 7- 



5. Cephalon with more strongly developed glabella, otherwise 



much like fig. 4. X 7- 



6. Cephalon with short intergenal spines and strongly marked 



glabella. X 5- 



7. Cephalon much like that of fig. 5, but without intergenal spine. 



X7. 



8. Usual form of fully developed cephalon. X 2. 



The above described figs, i to S were drawn for mc by Mr. 

 S. W. Ford from material in his collection obtained from the 

 vicinity of the City of Troy, New York. The drawings are 

 somewhat diagrammatic, but they serve to illustrate progres- 

 sive development of the form of the cephalon. The Ford col- 

 lection is now at the New York State Museum in Albany. 



Our fig. 9 represents a somewhat younger stage than Ford's 

 fig. I ; fig. 10 corresponds to Ford's fig. 2. 



9. The youngest stage (Paraprotaspis) of growth of this species 



observed. X 25. Length four-fifths of one millimeter. U. S. 

 National Museum, Catalogue No. 1541^^. 



10. A cephalon 1.75 mm. in length. X IS- U- S. National Museum, 



Catalogue No. 15413/. 



Figures 9 and 10 are drawn from the same specimens as those 

 illustrated by Walcott, 1886, pi. 17, figs. 5 and 6, respectively. 

 The specimens are both from locality (27), near Troy, Rens- 

 selaer County, New York. 



11. A cephalon 2 mm. in length that is slightly more advanced in 



development than fig. 2. X 10. This cephalon comes in between 

 figs. 2 and 3 of the Ford series. Locality (29a), near Schodack 

 Landing, Rensselaer County, New York. U. S. National 

 Museum, Catalogue No. 15413^. 



12. A cephalon 4 mm. in length with glabella expanded toward its 



anterior lobe. X 3- Compare with fig. 7, pi. 24, which has a 

 very narrow glabella at its anterior lobe. This is about the 

 same stage as fig. 5 of Ford's series. Locality (27), near 

 Troy, Rensselaer County, New York. U. S. National Museum, 

 Catalogue No. 15413/;. 



