OASTROPODA 



irOillddf 1 



Hall. IM.V (Amer. .Ion, \ol.\lvm.p.-Jr.M M .unto shells 



(1 to 4 mm. in diameter), gregarious in habit, in form like i'i/r(litt*. It is ililiicult 

 to decide whether any of hundred- of -pecimens seen preserve the shell or not. 

 though we are inclined to regard them as casts of the interior. They are always 

 of a black or brownish color, with the surface perfectly smooth and generally 

 glossy. The principal and typical -pecies, M. in'irnnfiia Hall, seems to range from 

 the Trenton to the Devonian. 



The -hell- comprised in this somewhat doubtful genus are certainly not "embry- 

 onic volutions of bellerophontes," as supposed by Waagen, but they may be dwarfed 

 \aiietie- of -pocies of (.'i/rfolH>'* and perhaps of other genera. They usually occur 

 associated with large number- of c>flni, another genus of minute gastropods, the 

 specie- of which again may l)e but dwarfed forms of Holopea or Cyclonema and 

 and with very small species of Ctenwlonta and Cinlophorus. 

 :TINA, n. gen. (t'lrich.) (CyrtolHe* [part.|. Lindstrnm, 1884.) Symmetri- 

 cally involute, small thin shells, consisting of one and a half or two rapidly 

 ml., < mtiguous or free volutions, with rounded sides and a more or less well 



developed slit -band: aperture higher than wide, sinuate dorsally and somewhat 

 deeply emarginated in front of the slit-hand; marks of growth curving strongly 

 backward, more or less distinctly lamellose, with crenulated edges and, when 

 distant enough, traversed by small wrinkled longitudinal riblets. Type, Crytolites 

 I'lmellifrr Lindstrom. In the same work (Silurian Gastropoda of Gotland, pp. 82-84) 

 Lind-tfin de-cribe- three more - belonging to this genus, vi/.: Crytolilrs 



l>li-i> v and C. oMitjuus. In America the new genus is represented by 



I/// nitiilitlus I'lrich (Jour. Cin. Soc. Nat. Hi-t.. vol. ii, p. 12; 1879), a species of 

 the upper part of the Trenton group. 



Family I'll" T< >\Y \ IM'II 1 1 1 M 



mietnc. involute -hell-: aperture not abruptly expanded; outer lip ami 

 line- of growth with a broad or narrow dor-al -inn-: -lit and band wanting. 



n. gen.' Shell thin, -uhgloliose, closely coiled; volutions compressed 

 lor-o-ventrally. moderately embracing, rounded on the back, enlarging gradually. 

 not abruptly expanded at the aperture, umbilicu- open: aperture transverse, the 

 outer lip with a rather broad and not very deep median insinuation: >l it -band wanting. 



i- known the surface markings con-i-t of t ran -verse or growth line- only. 

 Type, / : <-<n 'int'ujuatus Whittield, I'pper ('ambrian. Wisconsin. /.'. jifitos 



Koke-i. from Lower Siluri.i i in Kurope. seems to have all the essential char- 



acters of this gr 



Muned for thai f rnU ploaerr la tb* (colacr of Ike nor t h t.r n *UM. Dr. lUvid Hale Of n. 



J**t*4*^<Jtt*M( l 'fa4- 



