MANUAL OF THE MOLLUSCA. 



f^hell resembles that of Tropidoleptus, but the dental processng 

 are not crenulated, nor distinctly separated from the area as hi 

 that genus. 



AjMPHici.TJisrA, Laube, 1865. 



Etymology, amplii, about, and dino, a slope. 



Type, A. dubia, Miinster (Producta). 



Shell inequivalve circular, excavated, smooth ; ventral valve 

 convex, beak short ; perforated ; dorsal concave ; hinge line very 

 short and suboblique ; area wanting ; deltidium triangular, dis- 

 tinct ; structure of the test fibrous, squamose ; externally 

 AmpMcUna resembles some Leptsense, the shell structure is very 

 similar. 



Distrihuiion, 2 species. St. Cassian, Austria. 



Calceola. " Within the last few years the researches of Pro- 

 fessors Suess and Lindstrom have thrown considerable doubt as 

 to this genus belonging to the Brachiopoda." . . *' If a bra- 

 chiopod it seems the most abnormal of all its genera." — David- 

 son (1865). 



Family YIII. — Lixguled^.* 



LiNGTJLELLA, Salter, 1866. 



Etymology, diminutive of Lingula. 



Type, Lingula Davisii, M'Coy. 



^' Shell nearly equivalve, broad oblong, the ventral valve 

 pointed, ivith a distinct pedicle-groove. Muscular sears strong, 

 nearly as in Oholus, but the pair of anterior retractors are more 

 linear than in Obolus, and the sliding muscles small, and not 

 quite external as in Oholus.^' — (Salter.) 



Distribution, 3 species. Lower Silurian. Ireland, Wales, 

 Norway. 



LiKGULEPis, Hall, 1863. 



Etymology, lingula, a little tongue ; lepis, a scale. 



Tyjje, Lingula pinniformis, Owen. 



Shell thin, subovate, or subtrigonal ; composition and struc- 

 ture as in Lingula. Yentral or larger valve with beak more or 

 less produced and pointed ; visceral scar trilobed, with a longi- 

 tudinal raised mesial line or septum — lateral divisions diverging, 

 and usually longer than the middle one ; dorsal or smaller valve 

 with the beak less produced than that of the other ; visceral 

 Bear flabelliform. 



Distrihuiion, 4 species. Silurian, America. 



* See p. 390. 



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