OXYSTOMATOUS AND ALLIED CRABS OF AMERICA 23 



LYREIDUS BAIRDII Smith 



Plate 5, Figures 5, 6 



Lyreidus bairdii S. I. Smith, Proc. U. S. Nat. Mas., vol. 3, p. 420, 1881 (type 

 locality, off Marthas Vineyard, Mass., 100 fathoms, station 873, Fish Hawk; 

 type, U. S. N. M. no. 213G3). 



Diagnosis. — Median frontal tooth longer than lateral. Antero- 

 lateral spines small. No spine on outer surface of arm or wrist; a 

 spine on upper edge of palm. 



Description. — Carapace about one and three-fourths times as long 

 as breadth at anterolateral angles, back of which it narrows only 

 slightly for half the length of the lateral margms, wliich then curve 

 regularly around to the articulation with the abdomen. The rostrum 

 or median tooth of the deeply tridentate front is acutely triangular 

 and longer than broad; lateral teeth narrower and a little shorter. 

 The orbital sinuses are nearly as deep as broad and broadly rounded 

 behind. Edge of anterolateral margin rounded but armed with a 

 spinule about one-tliird the way from the lateral to the anterior 

 angle, and in front of this spinule the carapace is suddenly narrowed 

 so that the margm in front of the spinule is concave in outKne as 

 seen from above. Posterior half of lateral margin marked by a 

 distinct carina, but the anterior half is smoothly rounded. The 

 eyestalks are narrowed to triangular tips, which scarcely reach the 

 tips of the lateral teeth of the front; eyes black, on outer and inferior 

 edge of stalks. 



Chelipeds nearly as long as carapace; carpus with a spine and some 

 granules on upper margin; propodus short and much compressed; 

 distal margin transverse and nearly as long as the length of the article; 

 dorsal edge thin and sharp, terminating in a sharp tooth near tlie 

 articulation of the dactylus; back of the tliin digital process the 

 inferior edge is armed with three to six teeth, decreasing in size 

 proximaUy. Dactylus compressed and very thin, the outer edge 

 regularly curved and sharp; prehensile edge sharp and sUghtly irregu- 

 lar in outline, but not dentate, although the opposing edge of the 

 propodus is armed with about five or six low teeth inside the "thumb". 

 Dactyls of first and second ambulatories long, narrow and tliin edged ; 

 carpus and propodus broader in first than in second. In the thu'd 

 pair the propodus is nearly tmce as broad as long, the inferior edge 

 expanded into a thhi, broad, lamellar process nearly as large as the 

 body of the article, and with a cihated and regularly curved margin 

 nearly semicircular in outline. Dactylus nearly as broad as 

 propodus, lamellar throughout, articulated at the upper end of proxi- 

 mal margin, wliich, below the articulation, is concave m outline and 

 ciliated to match the adjoining lamellar process of the propodus; 

 lateral margins naked and convex in outline, except near tip, which 

 is sharply acuminate. 



