LOWER SILURIAN. 



191 



the name, from the Latin malum, an apple), and having no arms, and the ambulacral 

 grooves irregularly radiating; another species is the Palxocystites tenuiradiatus B. 

 (Hall's Actinocrinus tenuiradiatus), which is common, and lias been detected in the 

 granular limestone of West Rutland (Am. Jour. Sci., III. iv. 133.) 



3. Mollusks. — (a.) Bryozoans. — Fig. 306 represents the Retepora incepta H., a 

 thin, reticulate coral, the surface of which, magnified, is shown in Fig. 306 o; Fig. 307, 



Figs. 304-316. 



315' 



Kadiates. — Fig. 304, Palaeocrinus srriatus ; 305, Malocystis Murchisoni. Mollusks. —3%, Rete- 

 pora incepta ; 307, Ptilodietya fenestrata ; 308, Orthis costalis ; 309, Lepta?na plicifera ; 310, 

 Rhynchonella plena; 311, Maclurea magna; 312, M. Logani(xK); 313, operculum of same ; 

 314, Scalites angulatus ; 315, Bellerophon rotundatus. Articulates. — 316, Leperditia Canaden- 

 sis, var. nana. 



Ptilodietya fenestrata H., a small branching species, covered with minute cells, and Fig. 

 307 a, the surface magnified. 



(b.) BracMopods. — Y\g. 308, Orthis costalis H. ; Fig. 309, Lepta-.na plicifera H. ; L. 

 incrassata H.; Fig. 310, Rhynchonella plena H. (a side-view), a very common species, it 

 almost constituting some beds of the limestone'. There are also several Lingulellje (L. 

 Lyelli B., L. Huronensis B., etc.); Orthis imperator B., a species nearly 1\ in. across, be- 

 sides several other species of the genus. 



(c.) Lamellihranchs. —Vanuxemia Montrealensis B., a species nearly 1J in. long, re- 

 lated to Avicula. 



id.) Gaxteropods. — Y'tg. 311, Maclurea magna, which is very abundant,and sometimes 

 has a diameter of eight inches; Fig. 312, Maclurea Lor/ani, showing the shell closed by 

 its operculum; Fig. 313, the operculum, inside-view; Fig. 314, Scalites anfjulatns Con.; 

 Fig. 315, Bellerophon (Bucania) rotundatus H. ; Pleurotomaria. Calyx B., near Montreal. 



(e.) Cephalopods. — Orthoceras recti-annulatum H ; O. tenuiseptum H., a large species, 

 with the septa thin and rather crowded; O. velox B., Montreal, Mingan Ids.; O. dif- 

 fident B., Mingan Ids. 



t. Articulates. — (a.) Trilobites. — Among the species there are Illmnus Arcturus 



