284 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



CALLAVIA CROSBYI, new species 

 Plate 28, Figs. 1-8 



Olcnellus (Holinia) broggcri Burr, igoo, American Geologist, Vol. 25, 

 pp. 43-44. (Specimens from North Weymouth described and dis- 

 cussed.) 



OlencUus ( Mcsonacis) asal^lioidrs Burr. 1900, Idem, p. 45. (Distorted 

 specimens of the cephalon found at North Weymouth are doubtfully 

 identified with this species and characterized.) 



OlencUus (Holmia) broggcri GR.An.M', 1900, Occasional Papers Boston Soe. 

 Nat. Hist., No. 4, Vol. i, pt. 3, pp. 662-664. pi. 33, tigs. la-j. (Described 

 and discussed.) 



Olcnellus (Mcsonacis) asaf>hoidcs ? Gr.\eau, 1900, Idem, pp. 667-669, pi. 

 34, figs. 2a-b. (Identification based on distorted cephalons of Callavia 

 crosbyi. ) 



Metadoxidcs viagnificus ? Grabau, 1900, Idem, p. 670, pi. 34, figs. 4-6, 

 (Fragments of spines referred to the species with reservation.) 



Callavia crosbyi "^s so similar to C. broggcri that the description 

 of the latter, except where the two forms differ in details, will sttf- 

 fice. These differences are: the stronger posterior marginal border; 

 the presence of a narrow, clearly defined ridge about the anterior 

 glabellar lobe in C. crosbyi; a stronger, broader pleural furrow in 

 the thorax ; and a relatively shorter extension of the pleurae beyond 

 the end of the furrow. The pygidium of C. crosbyi is not well 

 known, as the only specimen showing it is crushed and poorly pre- 

 served. The hypostomse [pi. 28, fig. 6, and pi. 27, fig. 2] are similar 

 as far as known. 



Callavia crosbyi difiiers from C burri in the outline and detail.s 

 of the glabella, larger palpebral lobes, and proportions of the glabella 

 and cheeks. 



The surface is finely granular and beautifully ornamented with a 

 network of fine, irregular, anastomosing ridges, as shown l)y fig. 7, 

 pi. 28. On the left side the elongate meshes of the network are seen 

 as they occur on the broad margin of the cephalon and on the right 

 side the fine network of the cheek below the eye ; this surface ex- 

 tends over the glabella, the posterior border of the cephalon, and the 

 thoracic segments, except on the curved extensions of the pleune 

 wlirre the meshes are coarser. 



The longest cephalon in tlie collection has a length of 58 mm. 

 and width of 126 mm. This indicates that the dorsal shield attained 

 a length of 32 cm. or more. 



Formation and Locality. — Lower Cambrian: (gn) associated 

 with Callavia burri in the dark, purplish siliceous shale of the Wey- 

 mouth formation on I'earl Street, North Weymouth. Norfolk County, 

 Massaclnisctts. 



