24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



CALODISCUS RETICULATUS Rasetti, new species 

 Plate 1, fig. 1 ; plate 7, figures 12-18 



Available material. — A few cephala, mostly fragmentary. 



Description. — Glabella divided by a deep, wide transverse fur- 

 row into two lobes. Anterior lobe subovate, very convex, anteriorly 

 sloping down almost vertically to the broad depression formed by 

 the coalescence of the axial and border furrows. Glabella constricted 

 at the transverse furrow. Posterior lobe widening backward from the 

 transverse furrow, rising steeply, extended well beyond the general 

 outline of the cephalon; seemingly rounded at the posterior end, 

 although this portion is not completely preserved in any of the speci- 

 mens. Occipital ring differentiated under the rearward glabellar exten- 

 sion, at least at the sides where it is directed rather backward than 

 inward. Cheeks very convex, at least posteriorly where they over- 

 hang the lateral border furrow. Border expanded medially as in 

 preceding species, slightly convex, narrowing toward the genal angle, 

 lacking tubercles. Posterior border set off by a wide, deep furrow, 

 rather wide in distal portion ; genal angle narrowly rounded, lacking 

 spine. 



Surface of test covered with raised lines forming a reticulate pat- 

 tern. The largest cephalon has a width of 10.5 mm and a length of 

 approximately 10 mm. 



Occurrence. — Collections cs-4 and U.S.G.S. 4216, North Chatham. 



Discussion. — This species is closely related to the preceding, dif- 

 fering in the deeper division of the glabella by a transverse furrow, 

 greater elevation of the two glabellar lobes, reticulate ornamentation, 

 and lack of tubercles on the border. Clearly the present species is 

 so strikingly different from Calodiscus lobatus that, were intermediate 

 forms unknown, reference to the genus would hardly be suggested. 

 However, when one considers the series Calodiscus lobatus, C. loba- 

 tus agnostoides, C. helena, C. fissifrons, and C. reticulatus, it appears 

 difficult to decide where to place a possible generic boundary. 



Types.— RoXoty^t: U.S.N.M. 146006. Paratypes: U.S.N.M. 

 146007 and 146008. 



CALODISCUS OCCIPITALIS Rasetti, new species 

 Plate 9, figures 22, 23 



Available material. — One cephalon. 



Description. — Cephalon semielliptical, of low convexity. Glabella 

 elevated above the cheeks, higher posteriorly, with little longitudinal 

 convexity, parallel-sided in the posterior two-thirds, anteriorly taper- 



