Bulletin of the Natural History Society of New Brunswick Volume 19-20 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1901 Excerpt: ... in front of the umbo than are the typical shells occurring in Assise E. 3e. It does not flake at the middle layer of the shell as A. abavia of the same assise, does. In Assise E.-id valves appear, which, by their oblate form and surface markings, may, without much doubt, be referred to this species. Not only are they broader than the Acrotheles of the lower assises, but they are larger, some valves attaining mm. in width. An exterior of a ventral which is nearly one-half wider than long, and an interior of a dorsal about a third wider than its length, are figured. In the examples from this horizon the ventrals show surface markings, hinge area and foramen; their interiors show crescentic grooves of the vascular trunks, and at the margin, prints of its branches. Some of the dorsals show the surface sculpture; others, which have the interior exposed, show' median and lateral ridges, vascular lines, etc. A. Avia-puteis. n. mut. PI. xv, figs. 5 a and b. This seems to be a variety of A. avia. It differs in the possession of a pair of pits, one of which lies on each side of the space between tlie foramen and the visceral callus, partly overlapping each. The visceral callus is quite short in this form and has but little prominence. The ridges on the surface of the valve are more regularly concentric than in the type, and more sharply cut; about ten are found in the space of one millemetre. The cardinal area is curved forward towards the top, and finely striated. The foramen is about a fifth of the length of the valve from the cardinal line, and the front of the callus about a third. Vascular trunks and branches are visible on the surface of the ventral valve as in the type. The dorsal valve does not sensibly differ from that of A. avia. Size.--The largest valve s...