92 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 78 



univalved carapace, possibly is not far removed, but the general 

 aspect of its known parts differs so greatly from the present genus 

 that anything like close affinities between the two seems highly 

 improbable. While Hymenocaris is generally and probably correctly 

 regarded as an early representative of the Phyllocarida, no such 

 relation is believed to fit the case of Mononotella. This genus, on the 

 contrary, seems too much like Indiana and its more immediate allies 

 to permit of wide separation; hence, like those genera, its systematic 

 position is believed to be with the Phyllopoda and nearer the Ostracoda 

 than the Phyllocarida. 



MONONOTELLA FUSIFORMIS (Matthew) 



Plate 8, Figures 22-25 



Primitia{?) fusiformis Matthew, Trans. New York Acad. Sci., vol. 14, 1895, 



p. 137, pi. 8, figures 3a, 36. 

 Indiana fusiformis Matthew, Canadian Rec. Sci., vol. 8, 1902, p. 461. 



Description. — Carapace oblique, acuminate-ovate in lateral view, 

 the anterior end tapering to an obtuse point, the posterior half com- 

 paratively broadly rounded, semielliptic, the post dorsal angle obtuse 

 but causing an appreciable angulation about the middle of the dorsal 

 half of the outline; dorsum nearly straight; ventral part of outline 

 very gently convex until it begins to turn rapidly upward around the 

 posterior end. Sides (?valves) strongly convex, turned inward along 

 the edges; gap wide at the ends, especially so at the posterior, narrow- 

 ing from either end toward the middle of the ventral side. Test thin, 

 black, minutely punctate; punctae rather closely arranged, but not 

 sufficiently so to suggest reticulation. 



Dimensions of a nearly complete carapace: Greatest length about 

 7.0 mm., greatest width (at right angles to greatest length) 4.0 mm., 

 greatest thickness about 4.0 mm. 



Remarks.- — The single example (a left valve) of this species in the 

 Matthew collection of types is so different in its outline from all the 

 other Cambrian Conchostraca that it was recognized at once. The 

 narrower and almost acute anterior extremity characterizing the 

 species, while not perfectly preserved in the type specimen, is yet very 

 nearly complete. From this species alone it was not possible to 

 decide as to which is the ventral and which the dorsal side. Matthew 

 referred to it somewhat doubtfully as a right valve, but on comparison 

 with a more complete carapace, it proved to be a left side. Matthew 

 based his view chiefly on what he took to be obscure eye tubercles, 

 and a shallow groove running from them two-thirds across the valve. 

 Ho noted further a filiform fold at the posterior margin. None of 

 these features, however, is believed to be normal. On the contrary, 

 they are thought to have been effected by accidental distortion of the 

 pliable test. Similar fortuitous elevations and grooves are common 



