19 113 Atrypa reticularis, Linné (interior) Shaly limestone Lower Helderberg group. Clarksville, N.Y. 114 Platiceras obsum, Hall. Shaly limestone Lower Helderberg group. Clarksville, N.Y. 115 Platyceras spirale Hall Shaly limestone Lower Helderberg group. Clarksville, N.Y. 116 Platyceras robustum, Hall. Shaly limestone Lower Helderberg group. Clarksville, N.Y. 117 Platyceras retrorsum? Hall. Shaly limestone Lower Helderberg group. Clarksville, N.Y. 118 Platyceras platystomoidalis, Shaly limestone Lower Helderberg group. Clarksville, N.Y. 119 Platyceras ventricosum, Conrad Shaly limestone (3) Lower Helderberg group. Clarksville, N.Y. 120 Platyceras multisinuaturn, Hall. Shaly limestone Lower Helderberg group. Clarksville, N.Y. 121 Platyceras unguiforme, Hall Shaly limestone Lower Helderberg group. Clarksville, N.Y. 122 Platyceras curvirostrum, Hall. Shaly limestone Lower Helderberg group. Clarksville, N.Y. 123 Platyceras unguiforme, Hall. Lower Helderberg group. Jerusalem Hill, N.Y. 124 Platyceras bisulcatum, Hall Shaly limestone Lower Helderberg group. Clarksville, N.Y. 125 Platyceras lamellosum, Hall. Shaly limestone Lower Helderberg group. Clarksville, N.Y. 126 Platyceras n.sp. Shaly limestone Lower Helderberg group. Clarksville, N.Y.