Marylaxd Geological Survey 365 



Measurements of manus in millimeters 



Length 



Length exclusive 

 of finger 



29 



Width in 

 the middle 



19 



Thickness 



9.5 



18 



11 



6 



(a) — 



(b) 25 



The left cheliped of another specimen measures : Total length of manus, 

 27, palmar surface (without fingers) 20 mm.; width in middle 13 mm.; 

 greatest length of carpus, measured obliquely 20, or from middle of distal 

 to middle of proximal margin 14 mm.; width in middle 12 mm.; length 

 of merus 13 mm. (No. 10,005 Wagner Free Institute of Science, Mata- 

 wan formation of Crosswicks, N. J.) 



The abrupt deflection of the hind margin of the more convex face of the 

 manus and the downward bend, posteriorly, of its upper margin (as in 

 fig. 1) are characteristic of the species. 



Both chelae of a Lenola individual preserved in one nodule show the 

 right claw to be somewhat the larger. Otherwise the two claws seem to be 

 counterparts. I can find no other difference. 



It is an abundant species, known by remains of over one hundred indi- 

 viduals, chiefly the manus only, though sometimes all of the segments of 

 the cheliped are preserved in place ; when this is the case, it is usually due 

 to their being imbedded in hard nodules. No remains of the other limbs 

 or the body have been found. 



Specimens of the manus and carpus from Bohemia Creek are entirely 

 typical. One broad manus from Brooks estate and one from Post 218, 

 Chesapeake and Delaware Canal, differ in being broader, length of palm 

 18.3 mm., breadth 14.5 mm. I have seen a few examples of this broad 

 form from New Jersey and am uncertain about its status, whether it is 

 racial or possibly sexual. 



Two imperfect chelipeds, not very unlike in size, and in one nodule, were 

 formerly recorded by me as belonging to one individual ; but on renewed 

 examination I think them remains of two individuals. The smaller 

 cheliped of C. mortoni still remains unknown. 



Occurrence. — Matawan Formatiox. Post 218, Chesapeake and Dela- 

 ware Canal, Delaware ; Ulmstead Point, Anne Arundel County, Maryland. 

 Moxmouth Formatiox. Head of Bohemia Creek, Delaware; Brooks 

 estate near Seat Pleasant. Prince George's County, Maryland. 

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