52 PROCEEDINGS OF THE NATIONAL MUSEUM. ~ VOL. 37. 
hemisphere, and is chiefly found near tide limits on rocky shores. 
The specimens collected by Mr. Coker were very young, but seem to 
be referable to this species. 
MYTILUS GRANULATUS Hanley. 
Mytilus granulatus HANLEY, Proc. Zool. Soc. of London, for 1844, p. 17.—Gay, 
Hist. de Chile, vol. 8, 1854, p. 312, pl. 5, fig. 7. 
Abundant on the rocky shores of the island Lobos de Afuera. 
Distribution.—From Chiloé Island north to the Peruvian coast and 
islands. 
Shell small, trigonal, inflated, thick, yellowish-brown, radiately 
conspicuously and closely costate, the coste divaricating and bifur- 
cating; anterior end high, obtuse; posterior end dilated, obliquely 
truncated; interior whitish, with a crenulate margin; the cost are 
more or less distinctly granulate, and the form of the shell variable. 
This species has no economic importance. 
MODIOLUS GUYANENSIS Lamarck. 
Plats 27, fig. 2. 
Modiola guyanensis LAMARCK, An. s. Vert., vol. 6, 1819, p. 112.—RzEve, Conch. 
Iconica, vol. 10, Modiola, 1857, pl. 4, fig. 17. 
Mejillones. From the flats at Capon and at the mouth of the Tumbes River, 
embedded in soft mud. They are usually quite buried or covered with mud, but 
their presence can be recognized by slits in the mud, such as would be made by 
thrusting in a broad knife blade. They occur in the mud floor of mangrove swamps 
and are commonly used for food. 
Distribution.—Peru to the Gulf of California on the west, Guiana 
on the north, and south to Rio on the east coast of South America. 
This is one of the few species which occur on both the eastern, 
northern, and western shores of South America. It was described 
by Lamarck from Guiana; there is a specimen from Rio Janeiro, 
obtained by Anthony, in the National Collection, and we now have 
it from Guayaquil and Peru. 
Shell oblong, wedge shaped, externally green behind and above; 
the green area concentrically minutely wrinkled and separated from 
the rufous brown anterior part by a narrow lighter ray; ventral edge 
nearly straight, the interior pearly white, purple behind; the anterior 
end attenuated and the beaks adjacent. 
This is one of the most attractive species of the genus when in good 
condition. 
MODIOLUS ARCIFORMIS, new species. 
Plate 28, fig. 2. 
Huaquilla on the Ecuador border; apparently from a shellheap. 
Two fragments of a slender arcuate Modiolus were gathered with 
the other dead shells from the shore at this locality and appear to 
belong to an undescribed species. 
