66 THE NAUTILUS. 



DESCKIPTIONS OF TWO NEW SPECIES OF MUSCULIUM. 



BY V. STERKI. 



MUSCULTUM WINKLEYI, 11. Sp. 



Mussel slightly inequipartite, liigh, well and regularly inflated, 

 outlines along the valve edges well rounded to subcircular; posterior 

 part higher and somewhat larger than the anterior, often subtruncate 

 and with a slight postero-inferior angle; beaks little anterior, rather 

 narrow, calyculate or plain, prominent; somewhat inclined towards 

 the anterior; surface distinctly rugulose, du'lish or somewhat shining, 

 •with comparatively coarse, sharp, subregular, crowded concentric 

 striiB and some faint, shallow, irregular radial strige; color horn to 

 grayish or reddish, with one to a few narrow, darker zones along the 

 lin'is of growth, straw to light yellowish in the young, and in mar- 

 ginal zones becoming obsolete in old specimens; shell thin, subtrans- 

 lucent to opaque, hinge well curved, slight, cardinal teeth small, thin, 

 laterals with short cusps; ligament rather short, covered; scutum and 

 scutellum slightly but distinctly marked, rather long. 



Long. 8.5, alt. 7.8, diam. 5.4 mm. 



Soft parts not examined. 



Habitat: Old Orchard, Me.; vicinity of Danvers, Mass. 



M. winkleyi is not a variety or local form of some other species, 

 but markedly dilTerent and decidedly distinct. It has some resem- 

 blance to forms of M. securis Pr., but is higher, with more rounded 

 outlines, the hinge margin is more curved, the difference of size and 

 shape between the anterior and posterior parts is less marked; in 

 securis the posterior part is more truncate and less obliquely so to 

 the dorso-ventral line. All these differences are especially well 

 marked in half-grown specimens. 



It is somewhat variable: some specimens seen (years ago) from 

 Old Orchard were 10 and 10.5 mm. long; those seen from Danvers 

 are somewhat smaller and slighter, with slighter surface striae, some 

 of them of a little more angular outlines posteriorly. 



The type lot is No. 1396 of my collection of Sphceriidce^ from Old 

 Orchard, Me.,* collected and sent in 1896 by the Rev. H. W, Wink- 



' Now of the Carnegie Museum. 



' There is no doubt that specimens from the same place are in various other 

 collections as M. securis cardissum or as " ?." 



