152 PROCEEDINGS OF THE NATIONAL MUSEUM. tol. 37. 



hemisphere, and is chiefly found near tide limits on rocky shores. 

 The specimens collected by ]\Ir. 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, pi. 5, fig. 7. 

 Abundant on the rocky shores of the island Lobos de Afuera. 



Distribution. — From Chiloe Island north to the Peruvian coast and 

 islands. 



Shell small, trigonal, inflated, thick, yellowish-brown, radiately 

 conspicuously and closely costate, the costie (hvaricating and bifur- 

 cating; anterior end high, obtuse; posterior end dilated, obliquely 

 truncated; interior whitish, with a crenulate margin; the costse are 

 more or less distinctly granulate, and the form of the shell variable. 



This species has no economic importance. 



MODIOLUS GUYANENSIS Lamarck. 

 ^ Plate 27, fig. 2. 



Modiola guyanensis Lamarck, An. s. Vert., vol. 6, 1819, p. 112. — Reeve, Conch. 

 Iconica, vol. 10, Modiola, 1857, pi. 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 biu-ied 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. 



Distrihution. — Peru to the Gulf of California on the west, Guiana 

 on the north, and south to Kio 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 tlie most attractive species of the genus wdien 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. 



