122 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 56. 



The costal scutes are reduced in size, due to the enlargement of 

 the supramarginals. The second is much longer (fore and aft) than 

 broad, whereas this same scute in B. pnlchra is wider than long. 

 The area of the first costal scute is also greatly reduced, due prin- 

 cipally to the presence of an extra supramarginal which separates it 

 from contact with the marginals. There is a large subtriangular 

 supernumerary costal scute (see s. c. s., fig. 3) as in B. pulcTira and 

 such as is often present in other members of the Baenidae. 



The supramarginal scutes are 

 in a row, alternating with the 

 costal scutes, between them 

 and the marginals. These are 

 exceptionally wide, all except 

 the first being wider than long. 

 In the genotype the opposite 

 condition prevails. 



The marginal scutes are all 

 longer than high, and those 

 bordering the supramarginals 

 appear relatively wider than 

 in B. pnlchra. The marginal- 

 supramarginal sulcus back as 

 far as the eighth runs well 

 below the costo-peripheral su- 

 ture. On the fourth costal 

 this sulcus suddenly rises above 

 this suture. 



The plastron (fig. 4) is longer 

 than wide, with rather narrow 

 lobes. It has a greatest length 

 of 222 millimeters, with a 

 greatest breadth at the center 

 of 186 millimeters. The bridge 

 has a width fore and aft of 

 101 millimeters. The anterior lobe is 64 millimeters long and 94 

 millimeters wide at the base. The width diminishes quite rapidly 

 from the base anteriorly, the end being rounded with sinuous borders 

 caused by indentations where the sulci come to the edge. The pos- 

 terior lobe is 70 millimeters long and 84 millimeters wide at the base. 

 The lateral borders are nearly straight and convergent to the squarely 

 truncated end, that has a width of 45 millimeters. The lateral edges 

 are obtuse, but the bone thickens rapidly toward the median Ime. 

 Just behind the mguinal notch it reaches a thickness of 14 millimeters; 

 near the posterior extremity, 7 millimeters. 



FiQ. 4.— Plastron of Boremys albertensis, new 

 SPECIES. Type. No. 8803, U.S.N.M. ab., abdominal 

 scute; 071., ANAL SCUTE; ent., entoplastron; epi., 

 epiplastron; fern., femoral scute; g., gular scute; 

 hum., humeral scute; hyo., hyoplastron; hppo., 

 hypoplastron; ing., intergular; in. m., infra- 

 MAROiNAL scutes; meso., ME.S0PLASTR0N; pec, pec- 

 toral scutes; per., median peripherals; tiph., 



XIPHI PLASTRON. ONE-THIRD NATURAL .SIZE. 



