JflCRASTERIAS. 117 



y an ample, rounded, or oval sinus, sides produced and 

 e as the others; apex slightly convex. 



Diameter 12") ft. in centre ; ends 75 ft.; length 125 ft. 



First specimens were collected by H. S. Kitchel, in a pond, 

 Mt. Everett, Mass. It has occurred since in various places 

 in central and southern portions of New Jersey and Florida. 



The general outline of this species has some resemblance to 

 M. ad8cendem, Nord., found on the Sandwich Islands, but it 

 is larger, the polar lobe is more exserted, and hence the 

 sinuses between it and the basal lobes arc much wider and 

 deeper, broadly rounded, not "amplo-aeutangulo," and the an- 

 gles are not "bidentate," but are simply bifurcate. 



M. ai: f \t\. Bailey. Plate XXXVIII, fig. 5. 



Quadrangular; semicells three lobed ; the basal lobe- long 

 and arcuate, subtended by the transverse projections from the 

 ends of the slightly notched terminal lobes. 



Diameter 90-110 ft. 



Collected in Florida and described by Bailey. I have 

 found it repeatedly in New Jersey, Pennsylvania and Mas-a- 

 chusetts. 



M. expaxsa, Bailey. Plate XXXVII, fig. 12. 



Semicells three lobed ; basal lobe- subcorneal, lower mar- 

 ginal line regularly convex ; terminal lobe more -lender, 

 notched in the centre, spreading with an upward tendency to 

 an acute, often mucronate point. Usually smaller than the 

 preceding. 



Diameter about 75 ft. 



This form is near M. arcuata, but somewhat smaller, stouter, 

 with more regularly arched basal lobes ; apices more acute, 

 often mucronate. 



Habitat the same as the preceding. 



M. QUADEATA, Bailey. 



Described by the author as " Large quadrangular, three 

 lobed, basal lobes elongated, slightly curved, bidentate; ter- 

 minal lobes with two slender transverse bidentate projections." 



Diameter 110-120 u. 



t 



A species I have not recognized. 



