222 MAZATIAN UNITALVES 



Sab. — Panama, rare, C. B. Adams. — Mazatlan; extremely 

 rare ; L'pool Col. 



Tablet 1078 contains the two smallest specimens. — 1079, the 

 largest specimen. 



Genus EIMIJLA, Befr. 



Vide A. Ad. Monogr. Sim. in Proc. Zool. Soc. 1851, p. 226 :— 

 H. ^ A. Ad. Gen. vol. i. p. 451. — IS^on Eimula, Lowe, Proc. 

 Zool. Soc. 1854, p. 181. 



This beautiful genus is exactly intermediate between Fissu- 

 rella and Emarginula ; representing .permanently the j'oung 

 state of Fissurella, and, apparently, in its own .young state 

 resembling Emarginula. Like other Oolitic forms, it has 

 hitherto been found recent only in the Eastern Seas. 



281. Eimula Mazatla>'ica, n. s. 



a. t. parvd, ohlongd, cotnpressd, conicd ; alhidd, epidermide 

 tentii alho-fuscd indiitd ; apice planatd, angustd ; superfieie 

 tenue cancellatd, cancelUs quadratis ; fissurd suhelongatd, sub- 

 quadratd, intus subovali, callosd, exius interdum vix lobatd, ex 

 quadrante dimidium versus totm ah apice ad marginem longitu- 

 dinis continud ; foramine lineis incrementi decussato apicem 

 versus currente ; margine tenue crenulato. 



This shell would have been taken for the young of Glyphis 

 infequalis, which iu general appearance it greatly resembles ; 

 but that fortunately the yoiing of both that species and G. alta 

 were found, differing in the following particulars. In the 

 Glyphides, the hole is close to the apex, comparatively large 

 and solid,' and so arranged that as the hole increases, the apex 

 is eaten away. In the Eimulfc (of which 12 specimens were 

 found of different ages) the slit occupies a portion extending 

 from one-fourth to one-half of the entire length from apex to 

 margin ; and though the largest shell is much larger than the 

 Gh-phis, the apex still continues in the same relative position, 

 and there is a channel running up to the vertical portion, 

 shewing the lines of previous slits as in Pleurotomaria. The 

 lines of growth on the young shell seem to shew that at one 

 time it took the form of Emarginula, afterwards enclosing its 

 slit. In this respect it is the reverse of ScissureUa, which 

 (as appears from specimens found in the Teneriflfe dredgings) 

 when young is like Rimula or Trochotoma, when adult like 



