C. E. Beecher — Development of the Braehiopoda. 345 



a Les lobes du manteau commencent alors a se recouvrir d'une 

 cuticule epaisse et rigide que ne leur permet plus de se mouvoir 

 que dans le sens vertical." 



From the minuteness and the tenuous nature of the pro- 

 tegulum, its fossil preservation in an unaltered condition would 

 not be anticipated. Neither would it be found on the beaks 

 of mature shells, whether recent or fossil. In rare cases of 

 unusually perfect conservation of the beaks, the protegulum is 

 retained, but frequently its form and characters are exhibited 

 after its removal, by the impression left in the surrounding 

 calcareous test. To study the features of the protegulum, and 

 the early stages in the growth of the shell, it is very desirable 

 and often necessary to have young and well-preserved speci- 

 mens. The rapid encroachment of the pedicle on the ventral 

 beak commonly obliterates, at an early period, all traces of the 

 protegulum and early nepionic stages. While in the brachial 

 valve, abrasion from foreign objects, or against the deltidial 

 covering, or the pedicle itself, usually removes all early lines 

 of growth or nepionic characters. In general, fully matured 

 shells, recent or fossil, do not furnish material for a study of 

 the incipient growth stages. 



Affinities. — In looking for a prototype preserving throughout 

 its development the main features of the protegulum, and 

 showing no separate or distinct stages of growth, the early 

 primordial form hitherto known as Kutorgina, Billings, is at 

 once suggested. This genus, as shown below, includes two 

 distinct types, for one of which the name Faterina is proposed.* 



* The strict definition of Kutorgina limits it to calcareous shells, such as are 

 found near Swanton, Vermont, often occurring as casts in the limestone. The 

 original description of Obolella cingulata by Billings (Geology of Vermont, vol. ii, 

 p. 948, figs. 347-349, 1861) seems to include two species. One, represented by 

 figures 347 and 349 (loc. cit), agrees with phosphatic species having a straight 

 hinge line as long as the width of the shell. The other, shown in figure 348, has 

 a calcareous test, shorter hinge, flattened brachial valve, and convex pedicle 

 valve with arching beak. Upon the latter species, the genus was founded, and it 

 has been recognized as the type by C. D. Walcott (Bulletin U. S. Geol Surv., 

 No. 30, p. 102, pi. ix, figs. 1, la, b, 1886.) The species represented by Billings 

 in figures 347 and 349 resembles Obolus labradoricus (fig. 345, loc. cit.), and is 

 represented by Walcott (1. c , pi. ix, figs. 2, 2a, b) and referred by him also to 

 Kutorgina. Mr. Walcott recognizes two groups of species, which are classified 

 (p. 102) as: "shell structure calcareous (K. cingulata, K. Whitfieldi) or horny 

 {K. Labradorica, K. sculptilis)." 



An examination of specimens representing both groups, leads the writer to 

 consider Kutorgina cingulata and Obolus labradoricus of Billings as generically dis- 

 tinct. Therefore the name Paterina is here proposed to include species of the 

 type of Obolus labradoricus. This name is intended to express the primitive 

 ancestral characters which it possesses, Plate XVII, figures 1, 2. Exfoliated 

 specimens of Paterina labradorica show a roughened area on the cast, each side 

 of the median line near the beak. These probably represent muscular attach- 

 ments. Sections of the shell show no hinge area as described in K. cingulata. 

 A study of the latter would doubtless present distinct stages of growth. The 



