A Horntail Trilobite from McGregor, Iowa

Recently an excellent specimen of the horntail trilobite was collected at McGregor by Miss Florence S. Chapin a member of the geology field class of the McGregor Wild Life School. This fossil is so rarely found in other than fragmentary condition in Iowa that any well-preserved specimen deserves to be recorded and illustrated. The specimen presents the dorsal shield, is unrolled, and retains the head, thorax and pygidiurn or tail shield. The right margin of the head, the right free cheek and the tips of the tail spines are missing. When found only a part of the axial lobe and the ends of the pustules on the middle pleural segments were exposed. Careful treatment with potassium hydroxide and cautious use of needles and brushes have removed the limy covering. This cleaning process requires considerable time especially when the surface of a fossil, such as this one, presents so much relief