ON THINOCORUS AND ATTAGIS. 419 
therefore considered certain, aopenipaleniing the partial resemblance Page 417. 
of their vomers. = 
Next with reference to Chionis. By De Blainville this genus has 
been located close to Hematopus* ; and his view has been accepted, to 
a greater or less extent, by many. Nevertheless, although these 
_ birds are both strictly schizorhinal, their skulls give indications of a 
_ very different affinity. Hematopus possesses supraoccipital foramina, 
as well as pterygoid articulations with the basisphenoid, together with 
a bifid vomer, as represented in fig. 2. The similarly formed vomer is 
extraordinarily broad in Recurvirostra avocetta, which is shown in 
4 a “: 4 
; 
Anterior extremity of vomer in :—1l. Sterna hirundo ; 2. Hematopus ostralegus ; 
: 3. Numenius arquatus ; 4. Recurvirostra avocetta ; 5. Chionis alba. 
fig. 4, agreeing with the restricted Limicole; whilst in Chionis the 
vomer is blunt (fig. 5), and the basisphenoid rostrum, as well as the 
pterygoids, are entirely free as far as articulating facets are con- 
cerned. In the Bulletin of the United States National Museum+ Dr. 
_E. Coues and Mr. Kidder, after a most careful study of the whole 
anatomy of the genus, Chionis minor especially, remark, “ We find in 
Chionis a connecting link, closing the narrow gap between the plovers 
and gulls of the present day. In our opinion this group represents 
the survivors of an ancestral type from which both gulls and plovers 
have descended.”{ A separate division, termed Chionomorphea, is 
established for them, comparable with the Geranomorphe and the 
Cecomorphe of Prof. Huxley.§ My dissections of both C. alba and 
C. minor are quite in favour of this Larine affinity. That the genus 
deserves to be located in a separate division, however, as Dr. Coues 
suggests, I cannot agree. The Cecomorphe of Prof. Huxley include 
the Laride, Procellariide, Colymbide, and Alcide; and it is now 
known that neither the Procellariide nor Colymbide come near the 
Laride and Alcidw, which two last-named families are related one to 
* “ Annales des Sciences Naturelles,” vi. 1836, p. 97. 
< + No. 3, p. 85, Washington, 1876. t Loe. cit. p. 114. 
§ “ Proceedings of the Zoological Society,” 1867, p. 457. 
2.2.2 
